diff --git a/kotlin-native/runtime/src/main/kotlin/kotlin/text/Char.kt b/kotlin-native/runtime/src/main/kotlin/kotlin/text/Char.kt
index 991f49eb48b..0b43eadc2a8 100644
--- a/kotlin-native/runtime/src/main/kotlin/kotlin/text/Char.kt
+++ b/kotlin-native/runtime/src/main/kotlin/kotlin/text/Char.kt
@@ -150,6 +150,8 @@ public actual fun Char.isTitleCase(): Boolean {
 /**
  * Converts this character to upper case using Unicode mapping rules of the invariant locale.
  */
+@Deprecated("Use uppercaseChar() instead.", ReplaceWith("uppercaseChar()"))
+@DeprecatedSinceKotlin(warningSince = "1.5")
 public actual fun Char.toUpperCase(): Char = uppercaseCharImpl()
 
 /**
@@ -182,6 +184,8 @@ public actual fun Char.uppercase(): String = uppercaseImpl()
 /**
  * Converts this character to lower case using Unicode mapping rules of the invariant locale.
  */
+@Deprecated("Use lowercaseChar() instead.", ReplaceWith("lowercaseChar()"))
+@DeprecatedSinceKotlin(warningSince = "1.5")
 public actual fun Char.toLowerCase(): Char = lowercaseCharImpl()
 
 /**
diff --git a/kotlin-native/runtime/src/main/kotlin/kotlin/text/Strings.kt b/kotlin-native/runtime/src/main/kotlin/kotlin/text/Strings.kt
index f612e393f88..b13d48c0519 100644
--- a/kotlin-native/runtime/src/main/kotlin/kotlin/text/Strings.kt
+++ b/kotlin-native/runtime/src/main/kotlin/kotlin/text/Strings.kt
@@ -201,6 +201,8 @@ private fun String.unsafeRangeEqualsIgnoreCase(thisOffset: Int, other: String, o
 /**
  * Returns a copy of this string converted to upper case using the rules of the default locale.
  */
+@Deprecated("Use uppercase() instead.", ReplaceWith("uppercase()"))
+@DeprecatedSinceKotlin(warningSince = "1.5")
 public actual fun String.toUpperCase(): String = uppercaseImpl()
 
 /**
@@ -218,6 +220,8 @@ public actual fun String.uppercase(): String = uppercaseImpl()
 /**
  * Returns a copy of this string converted to lower case using the rules of the default locale.
  */
+@Deprecated("Use lowercase() instead.", ReplaceWith("lowercase()"))
+@DeprecatedSinceKotlin(warningSince = "1.5")
 public actual fun String.toLowerCase(): String = lowercaseImpl()
 
 /**
@@ -249,6 +253,8 @@ private external fun toCharArray(string: String, start: Int, size: Int): CharArr
  *
  * @sample samples.text.Strings.capitalize
  */
+@Deprecated("Use replaceFirstChar instead.", ReplaceWith("replaceFirstChar { if (it.isLowerCase()) it.titlecase() else it.toString() }"))
+@DeprecatedSinceKotlin(warningSince = "1.5")
 public actual fun String.capitalize(): String {
     return if (isNotEmpty() && this[0].isLowerCase()) substring(0, 1).toUpperCase() + substring(1) else this
 }
@@ -259,6 +265,8 @@ public actual fun String.capitalize(): String {
  *
  * @sample samples.text.Strings.decapitalize
  */
+@Deprecated("Use replaceFirstChar instead.", ReplaceWith("replaceFirstChar { it.lowercase() }"))
+@DeprecatedSinceKotlin(warningSince = "1.5")
 public actual fun String.decapitalize(): String {
     return if (isNotEmpty() && !this[0].isLowerCase()) substring(0, 1).toLowerCase() + substring(1) else this
 }