diff --git a/spring-web/src/main/java/org/springframework/web/multipart/support/DefaultMultipartHttpServletRequest.java b/spring-web/src/main/java/org/springframework/web/multipart/support/DefaultMultipartHttpServletRequest.java
index d80945e4bd..36fa283085 100644
--- a/spring-web/src/main/java/org/springframework/web/multipart/support/DefaultMultipartHttpServletRequest.java
+++ b/spring-web/src/main/java/org/springframework/web/multipart/support/DefaultMultipartHttpServletRequest.java
@@ -16,10 +16,13 @@
 
 package org.springframework.web.multipart.support;
 
+import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import javax.servlet.http.HttpServletRequest;
@@ -27,6 +30,7 @@ import javax.servlet.http.HttpServletRequest;
 import org.springframework.http.HttpHeaders;
 import org.springframework.lang.Nullable;
 import org.springframework.util.MultiValueMap;
+import org.springframework.util.StringUtils;
 import org.springframework.web.multipart.MultipartFile;
 
 /**
@@ -90,11 +94,20 @@ public class DefaultMultipartHttpServletRequest extends AbstractMultipartHttpSer
 
 	@Override
 	public String[] getParameterValues(String name) {
-		String[] values = getMultipartParameters().get(name);
-		if (values != null) {
-			return values;
+		String[] parameterValues = super.getParameterValues(name);
+		String[] mpValues = getMultipartParameters().get(name);
+		if (mpValues == null) {
+			return parameterValues;
+		}
+		if (parameterValues == null || getQueryString() == null) {
+			return mpValues;
+		}
+		else {
+			String[] result = new String[mpValues.length + parameterValues.length];
+			System.arraycopy(mpValues, 0, result, 0, mpValues.length);
+			System.arraycopy(parameterValues, 0, result, mpValues.length, parameterValues.length);
+			return result;
 		}
-		return super.getParameterValues(name);
 	}
 
 	@Override
@@ -105,25 +118,20 @@ public class DefaultMultipartHttpServletRequest extends AbstractMultipartHttpSer
 		}
 
 		Set<String> paramNames = new LinkedHashSet<>();
-		Enumeration<String> paramEnum = super.getParameterNames();
-		while (paramEnum.hasMoreElements()) {
-			paramNames.add(paramEnum.nextElement());
-		}
+		paramNames.addAll(Collections.list(super.getParameterNames()));
 		paramNames.addAll(multipartParameters.keySet());
 		return Collections.enumeration(paramNames);
 	}
 
 	@Override
 	public Map<String, String[]> getParameterMap() {
-		Map<String, String[]> multipartParameters = getMultipartParameters();
-		if (multipartParameters.isEmpty()) {
-			return super.getParameterMap();
+		Map<String, String[]> result = new LinkedHashMap<>();
+		Enumeration<String> names = getParameterNames();
+		while (names.hasMoreElements()) {
+			String name = names.nextElement();
+			result.put(name, getParameterValues(name));
 		}
-
-		Map<String, String[]> paramMap = new LinkedHashMap<>();
-		paramMap.putAll(super.getParameterMap());
-		paramMap.putAll(multipartParameters);
-		return paramMap;
+		return result;
 	}
 
 	@Override
diff --git a/spring-web/src/test/java/org/springframework/web/multipart/support/DefaultMultipartHttpServletRequestTests.java b/spring-web/src/test/java/org/springframework/web/multipart/support/DefaultMultipartHttpServletRequestTests.java
new file mode 100644
index 0000000000..fc2b964c88
--- /dev/null
+++ b/spring-web/src/test/java/org/springframework/web/multipart/support/DefaultMultipartHttpServletRequestTests.java
@@ -0,0 +1,89 @@
+/*
+ * Copyright 2002-2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.web.multipart.support;
+
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import org.junit.Test;
+
+import org.springframework.mock.web.test.MockHttpServletRequest;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
+
+import static org.junit.Assert.*;
+
+/**
+ * Unit tests for {@link DefaultMultipartHttpServletRequest}.
+ *
+ * @author Rossen Stoyanchev
+ */
+public class DefaultMultipartHttpServletRequestTests {
+
+	private final MockHttpServletRequest servletRequest = new MockHttpServletRequest();
+
+	private final Map<String, String[]> multipartParams = new LinkedHashMap<>();
+
+	private final MultiValueMap<String, String> queryParams = new LinkedMultiValueMap<>();
+
+
+	@Test // SPR-16590
+	public void parameterValues() {
+
+		this.multipartParams.put("key", new String[] {"p"});
+		this.queryParams.add("key", "q");
+
+		String[] values = createMultipartRequest().getParameterValues("key");
+
+		assertArrayEquals(new String[] {"p", "q"}, values);
+	}
+
+	@Test // SPR-16590
+	public void parameterMap() {
+
+		this.multipartParams.put("key1", new String[] {"p1"});
+		this.multipartParams.put("key2", new String[] {"p2"});
+
+		this.queryParams.add("key1", "q1");
+		this.queryParams.add("key3", "q3");
+
+		Map<String, String[]> map = createMultipartRequest().getParameterMap();
+
+		assertEquals(3, map.size());
+		assertArrayEquals(new String[] {"p1", "q1"}, map.get("key1"));
+		assertArrayEquals(new String[] {"p2"}, map.get("key2"));
+		assertArrayEquals(new String[] {"q3"}, map.get("key3"));
+	}
+
+	private DefaultMultipartHttpServletRequest createMultipartRequest() {
+		insertQueryParams();
+		return new DefaultMultipartHttpServletRequest(this.servletRequest, new LinkedMultiValueMap<>(),
+				this.multipartParams, new HashMap<>());
+	}
+
+	private void insertQueryParams() {
+		StringBuilder query = new StringBuilder();
+		for (String key : this.queryParams.keySet()) {
+			for (String value : this.queryParams.get(key)) {
+				this.servletRequest.addParameter(key, value);
+				query.append(query.length() > 0 ? "&" : "").append(key).append("=").append(value);
+			}
+		}
+		this.servletRequest.setQueryString(query.toString());
+	}
+
+}