diff --git a/icu4c/source/common/unicode/bytestriebuilder.h b/icu4c/source/common/unicode/bytestriebuilder.h
index a8412d3d6e..97814fcc6a 100644
--- a/icu4c/source/common/unicode/bytestriebuilder.h
+++ b/icu4c/source/common/unicode/bytestriebuilder.h
@@ -154,7 +154,6 @@ private:
         const char *s;
     };
     
-    // don't use #ifndef U_HIDE_INTERNAL_API with private class members or virtual methods.
     virtual Node *createLinearMatchNode(int32_t i, int32_t byteIndex, int32_t length,
                                         Node *nextNode) const;
 
diff --git a/icu4c/source/common/unicode/ucurr.h b/icu4c/source/common/unicode/ucurr.h
index e3831bba15..192bc298cf 100644
--- a/icu4c/source/common/unicode/ucurr.h
+++ b/icu4c/source/common/unicode/ucurr.h
@@ -102,8 +102,10 @@ typedef enum UCurrNameStyle {
      * currency, such as "US Dollar" for USD.
      * @stable ICU 2.6
      */
-    UCURR_LONG_NAME,
+    UCURR_LONG_NAME
 
+#ifndef U_HIDE_DRAFT_API
+    ,
     /**
      * Selector for getName() indicating the narrow currency symbol.
      * The narrow currency symbol is similar to the regular currency
@@ -113,6 +115,7 @@ typedef enum UCurrNameStyle {
      * @draft ICU 61
      */
     UCURR_NARROW_SYMBOL_NAME
+#endif  // U_HIDE_DRAFT_API
 } UCurrNameStyle;
 
 #if !UCONFIG_NO_SERVICE
diff --git a/icu4c/source/common/unicode/utf8.h b/icu4c/source/common/unicode/utf8.h
index 8fdedbd110..4bb063c5e3 100644
--- a/icu4c/source/common/unicode/utf8.h
+++ b/icu4c/source/common/unicode/utf8.h
@@ -609,6 +609,7 @@ utf8_back1SafeBody(const uint8_t *s, int32_t start, int32_t i);
     } \
 }
 
+#ifndef U_HIDE_DRAFT_API
 /**
  * If the string ends with a UTF-8 byte sequence that is valid so far
  * but incomplete, then reduce the length of the string to end before
@@ -657,6 +658,7 @@ utf8_back1SafeBody(const uint8_t *s, int32_t start, int32_t i);
             } \
         } \
     }
+#endif  // U_HIDE_DRAFT_API
 
 /* definitions with backward iteration -------------------------------------- */
 
diff --git a/icu4c/source/common/unicode/utypes.h b/icu4c/source/common/unicode/utypes.h
index edda5660d1..dd89f39acb 100644
--- a/icu4c/source/common/unicode/utypes.h
+++ b/icu4c/source/common/unicode/utypes.h
@@ -539,13 +539,15 @@ typedef enum UErrorCode {
     U_DEFAULT_KEYWORD_MISSING,        /**< Missing DEFAULT rule in plural rules */
     U_DECIMAL_NUMBER_SYNTAX_ERROR,    /**< Decimal number syntax error */
     U_FORMAT_INEXACT_ERROR,           /**< Cannot format a number exactly and rounding mode is ROUND_UNNECESSARY @stable ICU 4.8 */
+#ifndef U_HIDE_DRAFT_API
     U_NUMBER_ARG_OUTOFBOUNDS_ERROR,   /**< The argument to a NumberFormatter helper method was out of bounds; the bounds are usually 0 to 999. @draft ICU 61 */
+#endif  // U_HIDE_DRAFT_API
 #ifndef U_HIDE_DEPRECATED_API
     /**
      * One more than the highest normal formatting API error code.
      * @deprecated ICU 58 The numeric value may change over time, see ICU ticket #12420.
      */
-    U_FMT_PARSE_ERROR_LIMIT,
+    U_FMT_PARSE_ERROR_LIMIT = 0x10113,
 #endif  // U_HIDE_DEPRECATED_API
 
     /*
diff --git a/icu4c/source/i18n/unicode/dcfmtsym.h b/icu4c/source/i18n/unicode/dcfmtsym.h
index c9ff7a8018..59b79a70b9 100644
--- a/icu4c/source/i18n/unicode/dcfmtsym.h
+++ b/icu4c/source/i18n/unicode/dcfmtsym.h
@@ -406,8 +406,6 @@ public:
      * returning a const reference to one of the symbol strings.
      * The returned reference becomes invalid when the symbol is changed
      * or when the DecimalFormatSymbols are destroyed.
-     * ### TODO markus 2002oct11: Consider proposing getConstSymbol() to be really public.
-     * Note: moved #ifndef U_HIDE_INTERNAL_API after this, since this is needed for inline in DecimalFormat
      *
      * @param symbol Constant to indicate a number format symbol.
      * @return the format symbol by the param 'symbol'
@@ -501,7 +499,6 @@ DecimalFormatSymbols::getSymbol(ENumberFormatSymbol symbol) const {
     return *strPtr;
 }
 
-// See comments above for this function. Not hidden with #ifndef U_HIDE_INTERNAL_API
 inline const UnicodeString &
 DecimalFormatSymbols::getConstSymbol(ENumberFormatSymbol symbol) const {
     const UnicodeString *strPtr;
diff --git a/icu4c/source/i18n/unicode/decimfmt.h b/icu4c/source/i18n/unicode/decimfmt.h
index dcd4b7a329..dbc27d3a65 100644
--- a/icu4c/source/i18n/unicode/decimfmt.h
+++ b/icu4c/source/i18n/unicode/decimfmt.h
@@ -1970,12 +1970,14 @@ public:
     UCurrencyUsage getCurrencyUsage() const;
 
 
+#ifndef U_HIDE_DEPRECATED_API
     /**
      * The resource tags we use to retrieve decimal format data from
      * locale resource bundles.
      * @deprecated ICU 3.4. This string has no public purpose. Please don't use it.
      */
     static const char fgNumberPatterns[];
+#endif  // U_HIDE_DEPRECATED_API
 
 #ifndef U_HIDE_INTERNAL_API
     /**
diff --git a/icu4c/source/i18n/unicode/numberformatter.h b/icu4c/source/i18n/unicode/numberformatter.h
index 1152f154ed..3fbb33ccee 100644
--- a/icu4c/source/i18n/unicode/numberformatter.h
+++ b/icu4c/source/i18n/unicode/numberformatter.h
@@ -151,14 +151,17 @@ typedef enum UNumberUnitWidth {
      *
      * @draft ICU 60
      */
-            UNUM_UNIT_WIDTH_HIDDEN,
+            UNUM_UNIT_WIDTH_HIDDEN
 
+#ifndef U_HIDE_INTERNAL_API
+    ,
     /**
      * One more than the highest UNumberUnitWidth value.
      *
      * @internal ICU 60: The numeric value may change over time; see ICU ticket #12420.
      */
             UNUM_UNIT_WIDTH_COUNT
+#endif  // U_HIDE_INTERNAL_API
 } UNumberUnitWidth;
 
 /**
@@ -336,14 +339,17 @@ typedef enum UNumberSignDisplay {
      *
      * @draft ICU 61
      */
-    UNUM_SIGN_ACCOUNTING_EXCEPT_ZERO,
+    UNUM_SIGN_ACCOUNTING_EXCEPT_ZERO
 
+#ifndef U_HIDE_INTERNAL_API
+    ,
     /**
      * One more than the highest UNumberSignDisplay value.
      *
      * @internal ICU 60: The numeric value may change over time; see ICU ticket #12420.
      */
     UNUM_SIGN_COUNT
+#endif  // U_HIDE_INTERNAL_API
 } UNumberSignDisplay;
 
 /**
@@ -369,14 +375,17 @@ typedef enum UNumberDecimalSeparatorDisplay {
      *
      * @draft ICU 60
      */
-            UNUM_DECIMAL_SEPARATOR_ALWAYS,
+            UNUM_DECIMAL_SEPARATOR_ALWAYS
 
+#ifndef U_HIDE_INTERNAL_API
+    ,
     /**
      * One more than the highest UNumberDecimalSeparatorDisplay value.
      *
      * @internal ICU 60: The numeric value may change over time; see ICU ticket #12420.
      */
             UNUM_DECIMAL_SEPARATOR_COUNT
+#endif  // U_HIDE_INTERNAL_API
 } UNumberDecimalMarkDisplay;
 
 U_NAMESPACE_BEGIN namespace number {  // icu::number
@@ -395,6 +404,7 @@ class IntegerWidth;
 
 namespace impl {
 
+#ifndef U_HIDE_INTERNAL_API
 /**
  * Datatype for minimum/maximum fraction digits. Must be able to hold kMaxIntFracSig.
  *
@@ -409,6 +419,7 @@ typedef int16_t digits_t;
  * @internal
  */
 static constexpr int32_t DEFAULT_THRESHOLD = 3;
+#endif  // U_HIDE_INTERNAL_API
 
 // Forward declarations:
 class Padder;
@@ -1222,6 +1233,7 @@ class U_I18N_API IntegerWidth : public UMemory {
 
 namespace impl {
 
+// Do not enclose entire SymbolsWrapper with #ifndef U_HIDE_INTERNAL_API, needed for a protected field
 /** @internal */
 class U_I18N_API SymbolsWrapper : public UMemory {
   public:
@@ -1237,6 +1249,7 @@ class U_I18N_API SymbolsWrapper : public UMemory {
     /** @internal */
     SymbolsWrapper &operator=(const SymbolsWrapper &other);
 
+#ifndef U_HIDE_INTERNAL_API
     /**
      * The provided object is copied, but we do not adopt it.
      * @internal
@@ -1284,6 +1297,7 @@ class U_I18N_API SymbolsWrapper : public UMemory {
         }
         return FALSE;
     }
+#endif  // U_HIDE_INTERNAL_API
 
   private:
     enum SymbolsPointerType {
@@ -1300,9 +1314,11 @@ class U_I18N_API SymbolsWrapper : public UMemory {
     void doCleanup();
 };
 
+// Do not enclose entire Grouper with #ifndef U_HIDE_INTERNAL_API, needed for a protected field
 /** @internal */
 class U_I18N_API Grouper : public UMemory {
   public:
+#ifndef U_HIDE_INTERNAL_API
     /** @internal */
     static Grouper forStrategy(UGroupingStrategy grouping);
 
@@ -1311,6 +1327,7 @@ class U_I18N_API Grouper : public UMemory {
     /** @internal */
     Grouper(int16_t grouping1, int16_t grouping2, int16_t minGrouping)
             : fGrouping1(grouping1), fGrouping2(grouping2), fMinGrouping(minGrouping) {}
+#endif  // U_HIDE_INTERNAL_API
 
   private:
     /**
@@ -1352,14 +1369,17 @@ class U_I18N_API Grouper : public UMemory {
     friend class NumberFormatterImpl;
 };
 
+// Do not enclose entire Padder with #ifndef U_HIDE_INTERNAL_API, needed for a protected field
 /** @internal */
 class U_I18N_API Padder : public UMemory {
   public:
+#ifndef U_HIDE_INTERNAL_API
     /** @internal */
     static Padder none();
 
     /** @internal */
     static Padder codePoints(UChar32 cp, int32_t targetWidth, UNumberFormatPadPosition position);
+#endif  // U_HIDE_INTERNAL_API
 
   private:
     UChar32 fWidth;  // -3 = error; -2 = bogus; -1 = no padding
@@ -1409,6 +1429,7 @@ class U_I18N_API Padder : public UMemory {
     friend class impl::NumberFormatterImpl;
 };
 
+// Do not enclose entire MacroProps with #ifndef U_HIDE_INTERNAL_API, needed for a protected field
 /** @internal */
 struct U_I18N_API MacroProps : public UMemory {
     /** @internal */
diff --git a/icu4c/source/layoutex/layout/plruns.h b/icu4c/source/layoutex/layout/plruns.h
index 2a7a397d3e..6cbece8040 100644
--- a/icu4c/source/layoutex/layout/plruns.h
+++ b/icu4c/source/layoutex/layout/plruns.h
@@ -20,14 +20,17 @@
 
 /**
  * Opaque datatype representing an array of font runs
+ * @internal
  */
 typedef void pl_fontRuns;
 /**
  * Opaque datatype representing an array of value runs
+ * @internal
  */
 typedef void pl_valueRuns;
 /**
  * Opaque datatype representing an array of locale runs
+ * @internal
  */
 typedef void pl_localeRuns;