diff --git a/oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/client/JdbcRegisteredClientRepository.java b/oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/client/JdbcRegisteredClientRepository.java
index 558a4ae1..32e2442b 100644
--- a/oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/client/JdbcRegisteredClientRepository.java
+++ b/oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/client/JdbcRegisteredClientRepository.java
@@ -100,6 +100,8 @@ public class JdbcRegisteredClientRepository implements RegisteredClientRepositor
 			+ " WHERE " + PK_FILTER;
 	// @formatter:on
 
+	private static final String COUNT_REGISTERED_CLIENT_SQL = "SELECT COUNT(*) FROM " + TABLE_NAME + " WHERE ";
+
 	private final JdbcOperations jdbcOperations;
 	private RowMapper<RegisteredClient> registeredClientRowMapper;
 	private Function<RegisteredClient, List<SqlParameterValue>> registeredClientParametersMapper;
@@ -141,11 +143,31 @@ public class JdbcRegisteredClientRepository implements RegisteredClientRepositor
 	}
 
 	private void insertRegisteredClient(RegisteredClient registeredClient) {
+		assertUniqueIdentifiers(registeredClient);
 		List<SqlParameterValue> parameters = this.registeredClientParametersMapper.apply(registeredClient);
 		PreparedStatementSetter pss = new ArgumentPreparedStatementSetter(parameters.toArray());
 		this.jdbcOperations.update(INSERT_REGISTERED_CLIENT_SQL, pss);
 	}
 
+	private void assertUniqueIdentifiers(RegisteredClient registeredClient) {
+		Integer count = this.jdbcOperations.queryForObject(
+				COUNT_REGISTERED_CLIENT_SQL + "client_id = ?",
+				Integer.class,
+				registeredClient.getClientId());
+		if (count != null && count > 0) {
+			throw new IllegalArgumentException("Registered client must be unique. " +
+					"Found duplicate client identifier: " + registeredClient.getClientId());
+		}
+		count = this.jdbcOperations.queryForObject(
+				COUNT_REGISTERED_CLIENT_SQL + "client_secret = ?",
+				Integer.class,
+				registeredClient.getClientSecret());
+		if (count != null && count > 0) {
+			throw new IllegalArgumentException("Registered client must be unique. " +
+					"Found duplicate client secret for identifier: " + registeredClient.getId());
+		}
+	}
+
 	@Override
 	public RegisteredClient findById(String id) {
 		Assert.hasText(id, "id cannot be empty");
diff --git a/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/client/JdbcRegisteredClientRepositoryTests.java b/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/client/JdbcRegisteredClientRepositoryTests.java
index 24299967..e11e87e3 100644
--- a/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/client/JdbcRegisteredClientRepositoryTests.java
+++ b/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/client/JdbcRegisteredClientRepositoryTests.java
@@ -162,6 +162,40 @@ public class JdbcRegisteredClientRepositoryTests {
 		assertThat(registeredClient).isEqualTo(expectedRegisteredClient);
 	}
 
+	@Test
+	public void saveWhenExistingClientIdThenThrowIllegalArgumentException() {
+		RegisteredClient registeredClient1 = TestRegisteredClients.registeredClient()
+				.id("registration-1")
+				.clientId("client-1")
+				.build();
+		this.registeredClientRepository.save(registeredClient1);
+		RegisteredClient registeredClient2 = TestRegisteredClients.registeredClient()
+				.id("registration-2")
+				.clientId("client-1")
+				.build();
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> this.registeredClientRepository.save(registeredClient2))
+				.withMessage("Registered client must be unique. Found duplicate client identifier: " + registeredClient2.getClientId());
+	}
+
+	@Test
+	public void saveWhenExistingClientSecretThenThrowIllegalArgumentException() {
+		RegisteredClient registeredClient1 = TestRegisteredClients.registeredClient()
+				.id("registration-1")
+				.clientId("client-1")
+				.clientSecret("secret")
+				.build();
+		this.registeredClientRepository.save(registeredClient1);
+		RegisteredClient registeredClient2 = TestRegisteredClients.registeredClient()
+				.id("registration-2")
+				.clientId("client-2")
+				.clientSecret("secret")
+				.build();
+		assertThatIllegalArgumentException()
+				.isThrownBy(() -> this.registeredClientRepository.save(registeredClient2))
+				.withMessage("Registered client must be unique. Found duplicate client secret for identifier: " + registeredClient2.getId());
+	}
+
 	@Test
 	public void saveLoadRegisteredClientWhenCustomStrategiesSetThenCalled() throws Exception {
 		RowMapper<RegisteredClient> registeredClientRowMapper = spy(new RegisteredClientRowMapper());
diff --git a/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/client/TestRegisteredClients.java b/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/client/TestRegisteredClients.java
index aafd01d3..bf2c2640 100644
--- a/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/client/TestRegisteredClients.java
+++ b/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/client/TestRegisteredClients.java
@@ -31,7 +31,7 @@ public class TestRegisteredClients {
 		return RegisteredClient.withId("registration-1")
 				.clientId("client-1")
 				.clientIdIssuedAt(Instant.now().truncatedTo(ChronoUnit.SECONDS))
-				.clientSecret("secret")
+				.clientSecret("secret-1")
 				.authorizationGrantType(AuthorizationGrantType.AUTHORIZATION_CODE)
 				.authorizationGrantType(AuthorizationGrantType.REFRESH_TOKEN)
 				.clientAuthenticationMethod(ClientAuthenticationMethod.CLIENT_SECRET_BASIC)
@@ -43,7 +43,7 @@ public class TestRegisteredClients {
 		return RegisteredClient.withId("registration-2")
 				.clientId("client-2")
 				.clientIdIssuedAt(Instant.now().truncatedTo(ChronoUnit.SECONDS))
-				.clientSecret("secret")
+				.clientSecret("secret-2")
 				.authorizationGrantType(AuthorizationGrantType.AUTHORIZATION_CODE)
 				.authorizationGrantType(AuthorizationGrantType.REFRESH_TOKEN)
 				.authorizationGrantType(AuthorizationGrantType.CLIENT_CREDENTIALS)