diff --git a/icu4c/source/common/brkiter.cpp b/icu4c/source/common/brkiter.cpp
index b452cf2c050..12679c2f474 100644
--- a/icu4c/source/common/brkiter.cpp
+++ b/icu4c/source/common/brkiter.cpp
@@ -438,17 +438,14 @@ BreakIterator::makeInstance(const Locale& loc, int32_t kind, UErrorCode& status)
             UTRACE_ENTRY(UTRACE_UBRK_CREATE_LINE);
             uprv_strcpy(lb_lw, "line");
             UErrorCode kvStatus = U_ZERO_ERROR;
-            CharString value;
-            CharStringByteSink valueSink(&value);
-            loc.getKeywordValue("lb", valueSink, kvStatus);
+            auto value = loc.getKeywordValue<CharString>("lb", kvStatus);
             if (U_SUCCESS(kvStatus) && (value == "strict" || value == "normal" || value == "loose")) {
                 uprv_strcat(lb_lw, "_");
                 uprv_strcat(lb_lw, value.data());
             }
             // lw=phrase is only supported in Japanese and Korean
             if (uprv_strcmp(loc.getLanguage(), "ja") == 0 || uprv_strcmp(loc.getLanguage(), "ko") == 0) {
-                value.clear();
-                loc.getKeywordValue("lw", valueSink, kvStatus);
+                value = loc.getKeywordValue<CharString>("lw", kvStatus);
                 if (U_SUCCESS(kvStatus) && value == "phrase") {
                     uprv_strcat(lb_lw, "_");
                     uprv_strcat(lb_lw, value.data());
diff --git a/icu4c/source/common/bytesinkutil.h b/icu4c/source/common/bytesinkutil.h
index 3161b0d5cea..b3bd487be1d 100644
--- a/icu4c/source/common/bytesinkutil.h
+++ b/icu4c/source/common/bytesinkutil.h
@@ -43,6 +43,16 @@ private:
     CharString& dest_;
 };
 
+// CharString doesn't provide the public API that StringByteSink requires a
+// string class to have so this template specialization replaces the default
+// implementation of StringByteSink<CharString> with CharStringByteSink.
+template<>
+class StringByteSink<CharString> : public CharStringByteSink {
+ public:
+  StringByteSink(CharString* dest) : CharStringByteSink(dest) { }
+  StringByteSink(CharString* dest, int32_t /*initialAppendCapacity*/) : CharStringByteSink(dest) { }
+};
+
 class U_COMMON_API ByteSinkUtil {
 public:
     ByteSinkUtil() = delete;  // all static
diff --git a/icu4c/source/common/localebuilder.cpp b/icu4c/source/common/localebuilder.cpp
index e6871b2a8c0..e53065a8a60 100644
--- a/icu4c/source/common/localebuilder.cpp
+++ b/icu4c/source/common/localebuilder.cpp
@@ -3,7 +3,7 @@
 
 #include <utility>
 
-#include "bytesinkutil.h"  // CharStringByteSink
+#include "bytesinkutil.h"  // StringByteSink<CharString>
 #include "charstr.h"
 #include "cstring.h"
 #include "ulocimp.h"
@@ -183,9 +183,7 @@ _copyExtensions(const Locale& from, icu::StringEnumeration *keywords,
     }
     const char* key;
     while ((key = keywords->next(nullptr, errorCode)) != nullptr) {
-        CharString value;
-        CharStringByteSink sink(&value);
-        from.getKeywordValue(key, sink, errorCode);
+        auto value = from.getKeywordValue<CharString>(key, errorCode);
         if (U_FAILURE(errorCode)) { return; }
         if (uprv_strcmp(key, kAttributeKey) == 0) {
             transform(value.data(), value.length());
@@ -307,10 +305,8 @@ LocaleBuilder& LocaleBuilder::addUnicodeLocaleAttribute(
         return *this;
     }
 
-    CharString attributes;
-    CharStringByteSink sink(&attributes);
     UErrorCode localErrorCode = U_ZERO_ERROR;
-    extensions_->getKeywordValue(kAttributeKey, sink, localErrorCode);
+    auto attributes = extensions_->getKeywordValue<CharString>(kAttributeKey, localErrorCode);
     if (U_FAILURE(localErrorCode)) {
         CharString new_attributes(value_str.data(), status_);
         // No attributes, set the attribute.
@@ -362,9 +358,7 @@ LocaleBuilder& LocaleBuilder::removeUnicodeLocaleAttribute(
     }
     if (extensions_ == nullptr) { return *this; }
     UErrorCode localErrorCode = U_ZERO_ERROR;
-    CharString attributes;
-    CharStringByteSink sink(&attributes);
-    extensions_->getKeywordValue(kAttributeKey, sink, localErrorCode);
+    auto attributes = extensions_->getKeywordValue<CharString>(kAttributeKey, localErrorCode);
     // get failure, just return
     if (U_FAILURE(localErrorCode)) { return *this; }
     // Do not have any attributes, just return.
diff --git a/icu4c/source/common/locdspnm.cpp b/icu4c/source/common/locdspnm.cpp
index c836876658f..b2efddf4b40 100644
--- a/icu4c/source/common/locdspnm.cpp
+++ b/icu4c/source/common/locdspnm.cpp
@@ -634,13 +634,9 @@ LocaleDisplayNamesImpl::localeDisplayName(const Locale& loc,
     UnicodeString temp2;
     const char* key;
     while ((key = e->next((int32_t *)0, status)) != nullptr) {
-      CharString value;
-      {
-        CharStringByteSink sink(&value);
-        loc.getKeywordValue(key, sink, status);
-      }
-      if (U_FAILURE(status)) {
-        return result;
+        auto value = loc.getKeywordValue<CharString>(key, status);
+        if (U_FAILURE(status)) {
+            return result;
       }
       keyDisplayName(key, temp, true);
       temp.findAndReplace(formatOpenParen, formatReplaceOpenParen);
diff --git a/icu4c/source/common/locid.cpp b/icu4c/source/common/locid.cpp
index fcf59b660f5..4a84548b070 100644
--- a/icu4c/source/common/locid.cpp
+++ b/icu4c/source/common/locid.cpp
@@ -1521,13 +1521,12 @@ AliasReplacer::replaceTransformedExtensions(
     const char* tkey = ultag_getTKeyStart(str);
     int32_t tlangLen = (tkey == str) ? 0 :
         ((tkey == nullptr) ? len : static_cast<int32_t>((tkey - str - 1)));
-    CharStringByteSink sink(&output);
     if (tlangLen > 0) {
         Locale tlang = LocaleBuilder()
             .setLanguageTag(StringPiece(str, tlangLen))
             .build(status);
         tlang.canonicalize(status);
-        tlang.toLanguageTag(sink, status);
+        output = tlang.toLanguageTag<CharString>(status);
         if (U_FAILURE(status)) {
             return false;
         }
@@ -1728,9 +1727,7 @@ AliasReplacer::replace(const Locale& locale, CharString& out, UErrorCode& status
             while ((key = iter->next(nullptr, status)) != nullptr) {
                 if (uprv_strcmp("sd", key) == 0 || uprv_strcmp("rg", key) == 0 ||
                         uprv_strcmp("t", key) == 0) {
-                    CharString value;
-                    CharStringByteSink valueSink(&value);
-                    locale.getKeywordValue(key, valueSink, status);
+                    auto value = locale.getKeywordValue<CharString>(key, status);
                     if (U_FAILURE(status)) {
                         status = U_ZERO_ERROR;
                         continue;
@@ -2628,11 +2625,7 @@ Locale::getUnicodeKeywordValue(StringPiece keywordName,
         return;
     }
 
-    CharString legacy_value;
-    {
-        CharStringByteSink sink(&legacy_value);
-        getKeywordValue(legacy_key, sink, status);
-    }
+    auto legacy_value = getKeywordValue<CharString>(legacy_key, status);
 
     if (U_FAILURE(status)) {
         return;
diff --git a/icu4c/source/i18n/units_data.cpp b/icu4c/source/i18n/units_data.cpp
index 22859270b73..5160113d2b5 100644
--- a/icu4c/source/i18n/units_data.cpp
+++ b/icu4c/source/i18n/units_data.cpp
@@ -403,12 +403,8 @@ U_I18N_API UnitPreferences::UnitPreferences(UErrorCode &status) {
 }
 
 CharString getKeyWordValue(const Locale &locale, StringPiece kw, UErrorCode &status) {
-    CharString result;
-    if (U_FAILURE(status)) { return result; }
-    {
-        CharStringByteSink sink(&result);
-        locale.getKeywordValue(kw, sink, status);
-    }
+    if (U_FAILURE(status)) { return {}; }
+    auto result = locale.getKeywordValue<CharString>(kw, status);
     if (U_SUCCESS(status) && result.isEmpty()) {
         status = U_MISSING_RESOURCE_ERROR;
     }