diff --git a/core/src/main/java/org/mobilitydata/gtfsvalidator/notice/InvalidCharacterNotice.java b/core/src/main/java/org/mobilitydata/gtfsvalidator/notice/InvalidCharacterNotice.java
new file mode 100644
index 0000000000..428e09475a
--- /dev/null
+++ b/core/src/main/java/org/mobilitydata/gtfsvalidator/notice/InvalidCharacterNotice.java
@@ -0,0 +1,33 @@
+package org.mobilitydata.gtfsvalidator.notice;
+
+import static org.mobilitydata.gtfsvalidator.notice.SeverityLevel.ERROR;
+
+import org.mobilitydata.gtfsvalidator.annotation.GtfsValidationNotice;
+
+/**
+ * This field contains invalid characters, such as the replacement character ("\uFFFD").
+ *
+ * <p>Check that text was properly encoded in UTF-8 as required by GTFS.
+ */
+@GtfsValidationNotice(severity = ERROR)
+public class InvalidCharacterNotice extends ValidationNotice {
+  /** The name of the file containing the invalid characters. */
+  private final String filename;
+
+  /** The row number in the CSV file where the invalid characters were found. */
+  private final long csvRowNumber;
+
+  /** The name of the field containing the invalid characters. */
+  private final String fieldName;
+
+  /** The value of the field containing the invalid characters. */
+  private final String fieldValue;
+
+  public InvalidCharacterNotice(
+      String filename, long csvRowNumber, String fieldName, String fieldValue) {
+    this.filename = filename;
+    this.csvRowNumber = csvRowNumber;
+    this.fieldName = fieldName;
+    this.fieldValue = fieldValue;
+  }
+}
diff --git a/core/src/main/java/org/mobilitydata/gtfsvalidator/parsing/RowParser.java b/core/src/main/java/org/mobilitydata/gtfsvalidator/parsing/RowParser.java
index e29f7b53c5..5a1f5bb469 100644
--- a/core/src/main/java/org/mobilitydata/gtfsvalidator/parsing/RowParser.java
+++ b/core/src/main/java/org/mobilitydata/gtfsvalidator/parsing/RowParser.java
@@ -23,23 +23,7 @@
 import java.util.function.Function;
 import javax.annotation.Nullable;
 import org.mobilitydata.gtfsvalidator.annotation.FieldLevelEnum;
-import org.mobilitydata.gtfsvalidator.notice.EmptyRowNotice;
-import org.mobilitydata.gtfsvalidator.notice.InvalidColorNotice;
-import org.mobilitydata.gtfsvalidator.notice.InvalidCurrencyNotice;
-import org.mobilitydata.gtfsvalidator.notice.InvalidDateNotice;
-import org.mobilitydata.gtfsvalidator.notice.InvalidFloatNotice;
-import org.mobilitydata.gtfsvalidator.notice.InvalidIntegerNotice;
-import org.mobilitydata.gtfsvalidator.notice.InvalidLanguageCodeNotice;
-import org.mobilitydata.gtfsvalidator.notice.InvalidRowLengthNotice;
-import org.mobilitydata.gtfsvalidator.notice.InvalidTimeNotice;
-import org.mobilitydata.gtfsvalidator.notice.InvalidTimezoneNotice;
-import org.mobilitydata.gtfsvalidator.notice.MissingRecommendedFieldNotice;
-import org.mobilitydata.gtfsvalidator.notice.MissingRequiredFieldNotice;
-import org.mobilitydata.gtfsvalidator.notice.NoticeContainer;
-import org.mobilitydata.gtfsvalidator.notice.NumberOutOfRangeNotice;
-import org.mobilitydata.gtfsvalidator.notice.TooManyRowsNotice;
-import org.mobilitydata.gtfsvalidator.notice.UnexpectedEnumValueNotice;
-import org.mobilitydata.gtfsvalidator.notice.ValidationNotice;
+import org.mobilitydata.gtfsvalidator.notice.*;
 import org.mobilitydata.gtfsvalidator.table.GtfsColumnDescriptor;
 import org.mobilitydata.gtfsvalidator.table.GtfsEnum;
 import org.mobilitydata.gtfsvalidator.type.GtfsColor;
@@ -137,6 +121,12 @@ public String asString(int columnIndex, GtfsColumnDescriptor columnDescriptor) {
               fileName, getRowNumber(), columnDescriptor.columnName()));
     }
     if (s != null) {
+      // Validate if the string contains invalid characters
+      if (containsInvalidCharacters(s)) {
+        noticeContainer.addValidationNotice(
+            new InvalidCharacterNotice(fileName, getRowNumber(), columnDescriptor.columnName(), s));
+      }
+
       s =
           fieldValidator.validateField(
               s,
@@ -146,6 +136,10 @@ public String asString(int columnIndex, GtfsColumnDescriptor columnDescriptor) {
     return s;
   }
 
+  private boolean containsInvalidCharacters(String string) {
+    return string.contains("\uFFFD");
+  }
+
   @Nullable
   public String asText(int columnIndex, GtfsColumnDescriptor columnDescriptor) {
     return asString(columnIndex, columnDescriptor);