diff --git a/spring-core/src/main/java/org/springframework/util/StringUtils.java b/spring-core/src/main/java/org/springframework/util/StringUtils.java
index 20100bb7b9..2b0032d97c 100644
--- a/spring-core/src/main/java/org/springframework/util/StringUtils.java
+++ b/spring-core/src/main/java/org/springframework/util/StringUtils.java
@@ -904,7 +904,10 @@ public abstract class StringUtils {
 	 * @param array1 the first array (can be {@code null})
 	 * @param array2 the second array (can be {@code null})
 	 * @return the new array ({@code null} if both given arrays were {@code null})
+	 * @deprecated as of 4.3.15, in favor of manual merging via {@link LinkedHashSet}
+	 * (with every entry included at most once, even entries within the first array)
 	 */
+	@Deprecated
 	@Nullable
 	public static String[] mergeStringArrays(@Nullable String[] array1, @Nullable String[] array2) {
 		if (ObjectUtils.isEmpty(array1)) {
@@ -1021,10 +1024,9 @@ public abstract class StringUtils {
 
 	/**
 	 * Take an array of strings and split each element based on the given delimiter.
-	 * A {@code Properties} instance is then generated, with the left of the
-	 * delimiter providing the key, and the right of the delimiter providing the value.
-	 * <p>Will trim both the key and value before adding them to the
-	 * {@code Properties} instance.
+	 * A {@code Properties} instance is then generated, with the left of the delimiter
+	 * providing the key, and the right of the delimiter providing the value.
+	 * <p>Will trim both the key and value before adding them to the {@code Properties}.
 	 * @param array the array to process
 	 * @param delimiter to split each element using (typically the equals symbol)
 	 * @return a {@code Properties} instance representing the array contents,
diff --git a/spring-core/src/test/java/org/springframework/util/StringUtilsTests.java b/spring-core/src/test/java/org/springframework/util/StringUtilsTests.java
index 8ccffe38a6..61e996b45d 100644
--- a/spring-core/src/test/java/org/springframework/util/StringUtilsTests.java
+++ b/spring-core/src/test/java/org/springframework/util/StringUtilsTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * 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.
@@ -443,6 +443,7 @@ public class StringUtilsTests {
 	}
 
 	@Test
+	@Deprecated
 	public void testMergeStringArrays() {
 		String[] input1 = new String[] {"myString2"};
 		String[] input2 = new String[] {"myString1", "myString2"};