diff --git a/icu4c/source/i18n/unicode/numberformatter.h b/icu4c/source/i18n/unicode/numberformatter.h
index caf98e3dfa6..56beb3692b9 100644
--- a/icu4c/source/i18n/unicode/numberformatter.h
+++ b/icu4c/source/i18n/unicode/numberformatter.h
@@ -80,6 +80,9 @@
  * This API is based on the <em>fluent</em> design pattern popularized by libraries such as Google's Guava. For
  * extensive details on the design of this API, read <a href="https://goo.gl/szi5VB">the design doc</a>.
  *
+ * <p>
+ * Note: To format monetary/currency values, specify the currency in the `.unit()` function.
+ *
  * @author Shane Carr
  */
 
diff --git a/icu4j/main/classes/core/src/com/ibm/icu/number/NumberFormatter.java b/icu4j/main/classes/core/src/com/ibm/icu/number/NumberFormatter.java
index 5c4583dde4b..ce7d0fecddf 100644
--- a/icu4j/main/classes/core/src/com/ibm/icu/number/NumberFormatter.java
+++ b/icu4j/main/classes/core/src/com/ibm/icu/number/NumberFormatter.java
@@ -61,6 +61,9 @@ import com.ibm.icu.util.ULocale;
  * Guava. For extensive details on the design of this API, read <a href="https://goo.gl/szi5VB">the
  * design doc</a>.
  *
+ * <p>
+ * Note: To format monetary/currency values, specify the currency in the `.unit()` function.
+ *
  * @author Shane Carr
  * @stable ICU 60
  */