diff --git a/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java b/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java
index 4121d9a8b5..69e31d51a4 100644
--- a/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java
+++ b/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java
@@ -57,6 +57,7 @@ import org.springframework.web.util.WebUtils;
  * @author Brian Clozel
  * @author Vedran Pavic
  * @author Sebastien Deleuze
+ * @author Sam Brannen
  * @since 1.0.2
  */
 public class MockHttpServletResponse implements HttpServletResponse {
@@ -602,20 +603,22 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	}
 
 	private void setHeaderValue(String name, Object value) {
-		if (setSpecialHeader(name, value)) {
+		boolean replaceHeader = true;
+		if (setSpecialHeader(name, value, replaceHeader)) {
 			return;
 		}
-		doAddHeaderValue(name, value, true);
+		doAddHeaderValue(name, value, replaceHeader);
 	}
 
 	private void addHeaderValue(String name, Object value) {
-		if (setSpecialHeader(name, value)) {
+		boolean replaceHeader = false;
+		if (setSpecialHeader(name, value, replaceHeader)) {
 			return;
 		}
-		doAddHeaderValue(name, value, false);
+		doAddHeaderValue(name, value, replaceHeader);
 	}
 
-	private boolean setSpecialHeader(String name, Object value) {
+	private boolean setSpecialHeader(String name, Object value, boolean replaceHeader) {
 		if (HttpHeaders.CONTENT_TYPE.equalsIgnoreCase(name)) {
 			setContentType(value.toString());
 			return true;
@@ -634,7 +637,12 @@ public class MockHttpServletResponse implements HttpServletResponse {
 		}
 		else if (HttpHeaders.SET_COOKIE.equalsIgnoreCase(name)) {
 			MockCookie cookie = MockCookie.parse(value.toString());
-			addCookie(cookie);
+			if (replaceHeader) {
+				setCookie(cookie);
+			}
+			else {
+				addCookie(cookie);
+			}
 			return true;
 		}
 		else {
@@ -657,6 +665,20 @@ public class MockHttpServletResponse implements HttpServletResponse {
 		}
 	}
 
+	/**
+	 * Set the {@code Set-Cookie} header to the supplied {@link Cookie},
+	 * overwriting any previous cookies.
+	 * @param cookie the {@code Cookie} to set
+	 * @since 5.1.10
+	 * @see #addCookie(Cookie)
+	 */
+	private void setCookie(Cookie cookie) {
+		Assert.notNull(cookie, "Cookie must not be null");
+		this.cookies.clear();
+		this.cookies.add(cookie);
+		doAddHeaderValue(HttpHeaders.SET_COOKIE, getCookieHeader(cookie), true);
+	}
+
 	@Override
 	public void setStatus(int status) {
 		if (!this.isCommitted()) {
diff --git a/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.java b/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.java
index f1ff821139..4be36a65dc 100644
--- a/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.java
+++ b/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.java
@@ -333,23 +333,36 @@ class MockHttpServletResponseTests {
 		assertThat(response.getStatus()).isEqualTo(HttpServletResponse.SC_NOT_FOUND);
 	}
 
+	/**
+	 * @since 5.1.10
+	 */
 	@Test
-	void setCookieHeaderValid() {
-		response.addHeader(HttpHeaders.SET_COOKIE, "SESSION=123; Path=/; Secure; HttpOnly; SameSite=Lax");
-		Cookie cookie = response.getCookie("SESSION");
-		assertThat(cookie).isNotNull();
-		boolean condition = cookie instanceof MockCookie;
-		assertThat(condition).isTrue();
-		assertThat(cookie.getName()).isEqualTo("SESSION");
-		assertThat(cookie.getValue()).isEqualTo("123");
-		assertThat(cookie.getPath()).isEqualTo("/");
-		assertThat(cookie.getSecure()).isTrue();
-		assertThat(cookie.isHttpOnly()).isTrue();
-		assertThat(((MockCookie) cookie).getSameSite()).isEqualTo("Lax");
+	void setCookieHeader() {
+		response.setHeader(HttpHeaders.SET_COOKIE, "SESSION=123; Path=/; Secure; HttpOnly; SameSite=Lax");
+		assertNumCookies(1);
+		assertPrimarySessionCookie("123");
+
+		// Setting the Set-Cookie header a 2nd time should overwrite the previous value
+		response.setHeader(HttpHeaders.SET_COOKIE, "SESSION=999; Path=/; Secure; HttpOnly; SameSite=Lax");
+		assertNumCookies(1);
+		assertPrimarySessionCookie("999");
 	}
 
 	@Test
-	void addMockCookie() {
+	void addCookieHeader() {
+		response.addHeader(HttpHeaders.SET_COOKIE, "SESSION=123; Path=/; Secure; HttpOnly; SameSite=Lax");
+		assertNumCookies(1);
+		assertPrimarySessionCookie("123");
+
+		// Adding a 2nd cookie header should result in 2 cookies.
+		response.addHeader(HttpHeaders.SET_COOKIE, "SESSION=999; Path=/; Secure; HttpOnly; SameSite=Lax");
+		assertNumCookies(2);
+		assertPrimarySessionCookie("123");
+		assertCookieValues("123", "999");
+	}
+
+	@Test
+	void addCookie() {
 		MockCookie mockCookie = new MockCookie("SESSION", "123");
 		mockCookie.setPath("/");
 		mockCookie.setDomain("example.com");
@@ -360,8 +373,35 @@ class MockHttpServletResponseTests {
 
 		response.addCookie(mockCookie);
 
+		assertNumCookies(1);
 		assertThat(response.getHeader(HttpHeaders.SET_COOKIE)).isEqualTo(("SESSION=123; Path=/; Domain=example.com; Max-Age=0; " +
 				"Expires=Thu, 01 Jan 1970 00:00:00 GMT; Secure; HttpOnly; SameSite=Lax"));
+
+		// Adding a 2nd Cookie should result in 2 Cookies.
+		response.addCookie(new MockCookie("SESSION", "999"));
+		assertNumCookies(2);
+		assertCookieValues("123", "999");
+	}
+
+	private void assertNumCookies(int expected) {
+		assertThat(this.response.getCookies()).hasSize(expected);
+	}
+
+	private void assertCookieValues(String... expected) {
+		assertThat(response.getCookies()).extracting(Cookie::getValue).containsExactly(expected);
+	}
+
+	private void assertPrimarySessionCookie(String expectedValue) {
+		Cookie cookie = this.response.getCookie("SESSION");
+		assertThat(cookie).isNotNull();
+		boolean condition = cookie instanceof MockCookie;
+		assertThat(condition).isTrue();
+		assertThat(cookie.getName()).isEqualTo("SESSION");
+		assertThat(cookie.getValue()).isEqualTo(expectedValue);
+		assertThat(cookie.getPath()).isEqualTo("/");
+		assertThat(cookie.getSecure()).isTrue();
+		assertThat(cookie.isHttpOnly()).isTrue();
+		assertThat(((MockCookie) cookie).getSameSite()).isEqualTo("Lax");
 	}
 
 }
diff --git a/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletResponse.java b/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletResponse.java
index 97a39464f4..3f992773b8 100644
--- a/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletResponse.java
+++ b/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletResponse.java
@@ -57,6 +57,7 @@ import org.springframework.web.util.WebUtils;
  * @author Brian Clozel
  * @author Vedran Pavic
  * @author Sebastien Deleuze
+ * @author Sam Brannen
  * @since 1.0.2
  */
 public class MockHttpServletResponse implements HttpServletResponse {
@@ -602,20 +603,22 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	}
 
 	private void setHeaderValue(String name, Object value) {
-		if (setSpecialHeader(name, value)) {
+		boolean replaceHeader = true;
+		if (setSpecialHeader(name, value, replaceHeader)) {
 			return;
 		}
-		doAddHeaderValue(name, value, true);
+		doAddHeaderValue(name, value, replaceHeader);
 	}
 
 	private void addHeaderValue(String name, Object value) {
-		if (setSpecialHeader(name, value)) {
+		boolean replaceHeader = false;
+		if (setSpecialHeader(name, value, replaceHeader)) {
 			return;
 		}
-		doAddHeaderValue(name, value, false);
+		doAddHeaderValue(name, value, replaceHeader);
 	}
 
-	private boolean setSpecialHeader(String name, Object value) {
+	private boolean setSpecialHeader(String name, Object value, boolean replaceHeader) {
 		if (HttpHeaders.CONTENT_TYPE.equalsIgnoreCase(name)) {
 			setContentType(value.toString());
 			return true;
@@ -634,7 +637,12 @@ public class MockHttpServletResponse implements HttpServletResponse {
 		}
 		else if (HttpHeaders.SET_COOKIE.equalsIgnoreCase(name)) {
 			MockCookie cookie = MockCookie.parse(value.toString());
-			addCookie(cookie);
+			if (replaceHeader) {
+				setCookie(cookie);
+			}
+			else {
+				addCookie(cookie);
+			}
 			return true;
 		}
 		else {
@@ -657,6 +665,20 @@ public class MockHttpServletResponse implements HttpServletResponse {
 		}
 	}
 
+	/**
+	 * Set the {@code Set-Cookie} header to the supplied {@link Cookie},
+	 * overwriting any previous cookies.
+	 * @param cookie the {@code Cookie} to set
+	 * @since 5.1.10
+	 * @see #addCookie(Cookie)
+	 */
+	private void setCookie(Cookie cookie) {
+		Assert.notNull(cookie, "Cookie must not be null");
+		this.cookies.clear();
+		this.cookies.add(cookie);
+		doAddHeaderValue(HttpHeaders.SET_COOKIE, getCookieHeader(cookie), true);
+	}
+
 	@Override
 	public void setStatus(int status) {
 		if (!this.isCommitted()) {