diff --git a/src/main/kotlin/kr/co/vividnext/sodalive/member/MemberController.kt b/src/main/kotlin/kr/co/vividnext/sodalive/member/MemberController.kt
index 74df0080..9aca5480 100644
--- a/src/main/kotlin/kr/co/vividnext/sodalive/member/MemberController.kt
+++ b/src/main/kotlin/kr/co/vividnext/sodalive/member/MemberController.kt
@@ -77,7 +77,7 @@ class MemberController(
         )
 
         val message = messageSource.getMessage("member.signup.success", langContext.lang)
-        return ApiResponse.ok(message = message, data = response.loginResponse)
+        return ApiResponse.ok(message = message, data = response.loginResponse.copy(isNew = true))
     }
 
     @PostMapping("/signup")
@@ -96,7 +96,7 @@ class MemberController(
         }
 
         val message = messageSource.getMessage("member.signup.success", langContext.lang)
-        return ApiResponse.ok(message = message, data = response.loginResponse)
+        return ApiResponse.ok(message = message, data = response.loginResponse.copy(isNew = true))
     }
 
     @PostMapping("/login")
@@ -440,7 +440,7 @@ class MemberController(
         }
 
         val message = messageSource.getMessage("member.signup.success", langContext.lang)
-        return ApiResponse.ok(message = message, data = response.loginResponse)
+        return ApiResponse.ok(message = message, data = response.loginResponse.copy(isNew = response.isNew))
     }
 
     private fun extractBearerToken(authHeader: String, provider: MemberProvider): String {
diff --git a/src/main/kotlin/kr/co/vividnext/sodalive/member/login/LoginResponse.kt b/src/main/kotlin/kr/co/vividnext/sodalive/member/login/LoginResponse.kt
index 667f06d8..4e7d3d26 100644
--- a/src/main/kotlin/kr/co/vividnext/sodalive/member/login/LoginResponse.kt
+++ b/src/main/kotlin/kr/co/vividnext/sodalive/member/login/LoginResponse.kt
@@ -1,9 +1,14 @@
 package kr.co.vividnext.sodalive.member.login
 
+import com.fasterxml.jackson.annotation.JsonProperty
+
 data class LoginResponse(
     val userId: Long,
     val token: String,
     val nickname: String,
     val email: String,
-    val profileImage: String
+    val profileImage: String,
+    @get:JsonProperty("isNew")
+    @param:JsonProperty("isNew")
+    val isNew: Boolean = false
 )
diff --git a/src/test/kotlin/kr/co/vividnext/sodalive/member/MemberLoginResponseContractTest.kt b/src/test/kotlin/kr/co/vividnext/sodalive/member/MemberLoginResponseContractTest.kt
new file mode 100644
index 00000000..4d1513e7
--- /dev/null
+++ b/src/test/kotlin/kr/co/vividnext/sodalive/member/MemberLoginResponseContractTest.kt
@@ -0,0 +1,219 @@
+package kr.co.vividnext.sodalive.member
+
+import com.fasterxml.jackson.databind.JsonNode
+import com.fasterxml.jackson.databind.ObjectMapper
+import kr.co.vividnext.sodalive.common.ApiResponse
+import kr.co.vividnext.sodalive.creator.admin.member.CreatorAdminMemberService
+import kr.co.vividnext.sodalive.marketing.AdTrackingHistoryType
+import kr.co.vividnext.sodalive.marketing.AdTrackingService
+import kr.co.vividnext.sodalive.member.login.LoginRequest
+import kr.co.vividnext.sodalive.member.login.LoginResponse
+import kr.co.vividnext.sodalive.member.signUp.SignUpRequestV2
+import kr.co.vividnext.sodalive.member.signUp.SignUpResponse
+import kr.co.vividnext.sodalive.member.social.SocialAuthService
+import kr.co.vividnext.sodalive.member.social.SocialAuthServiceResolver
+import kr.co.vividnext.sodalive.member.social.SocialLoginResponse
+import kr.co.vividnext.sodalive.support.EmbeddedRedisInitializer
+import kr.co.vividnext.sodalive.useraction.ActionType
+import kr.co.vividnext.sodalive.useraction.UserActionService
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertFalse
+import org.junit.jupiter.api.Assertions.assertTrue
+import org.junit.jupiter.api.DisplayName
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.CsvSource
+import org.junit.jupiter.params.provider.ValueSource
+import org.mockito.Mockito
+import org.springframework.beans.factory.annotation.Autowired
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc
+import org.springframework.boot.test.context.SpringBootTest
+import org.springframework.boot.test.mock.mockito.MockBean
+import org.springframework.http.MediaType
+import org.springframework.mock.web.MockMultipartFile
+import org.springframework.test.context.ContextConfiguration
+import org.springframework.test.web.servlet.MockMvc
+import org.springframework.test.web.servlet.request.MockHttpServletRequestBuilder
+import org.springframework.test.web.servlet.request.MockMvcRequestBuilders.multipart
+import org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post
+import org.springframework.test.web.servlet.result.MockMvcResultMatchers.status
+
+@SpringBootTest
+@AutoConfigureMockMvc
+@ContextConfiguration(initializers = [EmbeddedRedisInitializer::class])
+class MemberLoginResponseContractTest @Autowired constructor(
+    private val mockMvc: MockMvc,
+    private val objectMapper: ObjectMapper
+) {
+    @MockBean
+    private lateinit var memberService: MemberService
+
+    @MockBean
+    private lateinit var creatorAdminMemberService: CreatorAdminMemberService
+
+    @MockBean
+    private lateinit var socialAuthServiceResolver: SocialAuthServiceResolver
+
+    @MockBean
+    private lateinit var trackingService: AdTrackingService
+
+    @MockBean
+    private lateinit var userActionService: UserActionService
+
+    private val loginResponse = LoginResponse(42L, "issued-token", "member", "", "profile-url")
+
+    @ParameterizedTest(name = "{0} isNew={1}")
+    @CsvSource(
+        "GOOGLE, false",
+        "GOOGLE, true",
+        "KAKAO, false",
+        "KAKAO, true",
+        "APPLE, false",
+        "APPLE, true",
+        "LINE, false",
+        "LINE, true"
+    )
+    @DisplayName("모든 소셜 로그인은 내부 가입 여부와 기존 JSON 계약 및 부수 동작을 유지한다")
+    fun shouldExposeSocialIsNewAsBooleanForEveryProvider(provider: MemberProvider, isNew: Boolean) {
+        val authService = Mockito.mock(SocialAuthService::class.java)
+        val nonce = if (provider == MemberProvider.APPLE || provider == MemberProvider.LINE) "login-nonce" else null
+        Mockito.`when`(socialAuthServiceResolver.resolve(provider)).thenReturn(authService)
+        Mockito.`when`(authService.authenticate("provider-token", "web", "campaign-pid", "push-token", nonce))
+            .thenReturn(SocialLoginResponse(42L, "campaign-pid", loginResponse, isNew))
+
+        val request = post("/member/login/${provider.name.lowercase()}")
+            .contentType(MediaType.APPLICATION_JSON)
+            .content(
+                """{
+                    "container":"web", "marketingPid":"campaign-pid", "pushToken":"push-token",
+                    "identityToken":"provider-token", "nonce":"login-nonce"
+                }"""
+            )
+        if (nonce == null) request.header("Authorization", "Bearer provider-token")
+
+        val response = perform(request)
+
+        Mockito.verify(authService).authenticate("provider-token", "web", "campaign-pid", "push-token", nonce)
+        Mockito.verify(trackingService).saveTrackingHistory("campaign-pid", AdTrackingHistoryType.SIGNUP, 42L)
+        Mockito.verify(userActionService, Mockito.times(if (isNew) 1 else 0))
+            .recordAction(42L, false, ActionType.SIGN_UP)
+        Mockito.verifyNoMoreInteractions(trackingService, userActionService)
+        assertEnvelope(response, "Congratulations on your sign up.")
+        assertLoginData(response.path("data"), isNew)
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = ["/member/signup", "/member/signup/v2"])
+    @DisplayName("두 이메일 가입 응답은 서비스 DTO 기본값과 무관하게 신규 회원 여부를 true로 반환한다")
+    fun shouldReturnNewForBothEmailSignupEndpoints(path: String) {
+        val signupResponse = SignUpResponse(42L, "campaign-pid", loginResponse)
+        val request = if (path == "/member/signup") {
+            val body = """{
+                "email":"member@test.com", "password":"test-password", "nickname":"member", "gender":"NONE",
+                "marketingPid":"campaign-pid", "isAgreeTermsOfService":true, "isAgreePrivacyPolicy":true, "container":"web"
+            }"""
+            Mockito.`when`(memberService.signUp(null, body)).thenReturn(signupResponse)
+            multipart(path).file(MockMultipartFile("request", "", MediaType.TEXT_PLAIN_VALUE, body.toByteArray()))
+        } else {
+            Mockito.`when`(
+                memberService.signUpV2(
+                    SignUpRequestV2(
+                        email = "member@test.com",
+                        password = "test-password",
+                        marketingPid = "campaign-pid",
+                        isAgreeTermsOfService = true,
+                        isAgreePrivacyPolicy = true,
+                        container = "web"
+                    )
+                )
+            ).thenReturn(signupResponse)
+            post(path).contentType(MediaType.APPLICATION_JSON).content(
+                """{
+                    "email":"member@test.com", "password":"test-password", "marketingPid":"campaign-pid",
+                    "isAgreeTermsOfService":true, "isAgreePrivacyPolicy":true, "container":"web"
+                }"""
+            )
+        }
+
+        val response = perform(request)
+
+        Mockito.verify(trackingService).saveTrackingHistory("campaign-pid", AdTrackingHistoryType.SIGNUP, 42L)
+        Mockito.verify(userActionService, Mockito.times(if (path == "/member/signup/v2") 1 else 0))
+            .recordAction(42L, false, ActionType.SIGN_UP)
+        Mockito.verifyNoMoreInteractions(trackingService, userActionService)
+        assertEnvelope(response, "Congratulations on your sign up.")
+        assertLoginData(response.path("data"), true)
+    }
+
+    @ParameterizedTest(name = "isAdmin={0}, isCreator={1}")
+    @CsvSource("false, false", "true, false", "false, true")
+    @DisplayName("일반 및 관리자 및 크리에이터 회원 로그인은 신규 회원 여부를 false로 반환한다")
+    fun shouldReturnFalseForEveryMemberLoginBranch(isAdmin: Boolean, isCreator: Boolean) {
+        val request = LoginRequest("member@test.com", "test-password", isAdmin, isCreator)
+        Mockito.`when`(memberService.login(request))
+            .thenReturn(ApiResponse.ok(data = loginResponse, message = "You are logged in."))
+
+        val response = perform(
+            post("/member/login").contentType(MediaType.APPLICATION_JSON).content(
+                """{"email":"member@test.com","password":"test-password","isAdmin":$isAdmin,"isCreator":$isCreator}"""
+            )
+        )
+
+        Mockito.verify(memberService).login(request)
+        assertEnvelope(response, "You are logged in.")
+        assertLoginData(response.path("data"), false)
+    }
+
+    @Test
+    @DisplayName("크리에이터 관리자 로그인은 공유 응답의 신규 회원 여부를 false로 반환한다")
+    fun shouldReturnFalseForCreatorAdminLogin() {
+        val request = LoginRequest("member@test.com", "test-password")
+        Mockito.`when`(creatorAdminMemberService.login(request))
+            .thenReturn(ApiResponse.ok(data = loginResponse, message = "Logged in."))
+
+        val response = perform(
+            post("/creator-admin/member/login").contentType(MediaType.APPLICATION_JSON)
+                .content("""{"email":"member@test.com","password":"test-password"}""")
+        )
+
+        Mockito.verify(creatorAdminMemberService).login(request)
+        assertEnvelope(response, "Logged in.")
+        assertLoginData(response.path("data"), false)
+    }
+
+    @Test
+    @DisplayName("애플리케이션 Jackson은 기본 LoginResponse의 isNew false를 생략하지 않는다")
+    fun shouldSerializeDefaultLoginResponseWithIsNewFalse() {
+        assertLoginData(objectMapper.readTree(objectMapper.writeValueAsString(loginResponse)), false)
+    }
+
+    private fun perform(request: MockHttpServletRequestBuilder): JsonNode {
+        val response = mockMvc.perform(request.header("Accept-Language", "en"))
+            .andExpect(status().isOk)
+            .andReturn().response
+        return objectMapper.readTree(response.contentAsByteArray)
+    }
+
+    private fun assertEnvelope(response: JsonNode, message: String) {
+        assertEquals(setOf("success", "message", "data", "errorProperty"), response.fieldNames().asSequence().toSet())
+        assertTrue(response.path("success").isBoolean)
+        assertTrue(response.path("success").booleanValue())
+        assertEquals(message, response.path("message").textValue())
+        assertTrue(response.path("errorProperty").isNull)
+    }
+
+    private fun assertLoginData(data: JsonNode, isNew: Boolean) {
+        assertTrue(data.path("isNew").isBoolean, "isNew must be a present JSON boolean: $data")
+        assertEquals(isNew, data.path("isNew").booleanValue())
+        assertFalse(data.has("new"))
+        assertEquals(
+            setOf("userId", "token", "nickname", "email", "profileImage", "isNew"),
+            data.fieldNames().asSequence().toSet()
+        )
+        assertEquals(42L, data.path("userId").longValue())
+        assertEquals("issued-token", data.path("token").textValue())
+        assertEquals("member", data.path("nickname").textValue())
+        assertEquals("", data.path("email").textValue())
+        assertEquals("profile-url", data.path("profileImage").textValue())
+    }
+}