diff --git a/.changeset/wet-ears-scream.md b/.changeset/wet-ears-scream.md
new file mode 100644
index 00000000000..86e05fb9a75
--- /dev/null
+++ b/.changeset/wet-ears-scream.md
@@ -0,0 +1,5 @@
+---
+'@itwin/itwinui-react': patch
+---
+
+`DatePicker` with `enableRangeSelect` now allows `startDate` and `endDate` to *both* be `undefined` (e.g. when there is no initial range). Passing `Date` to just *one* of them is not allowed.
diff --git a/packages/itwinui-react/src/core/DatePicker/DatePicker.tsx b/packages/itwinui-react/src/core/DatePicker/DatePicker.tsx
index 9b5b873b8c0..304c14ddaba 100644
--- a/packages/itwinui-react/src/core/DatePicker/DatePicker.tsx
+++ b/packages/itwinui-react/src/core/DatePicker/DatePicker.tsx
@@ -13,6 +13,7 @@ import {
   Box,
   useId,
   useLayoutEffect,
+  useWarningLogger,
 } from '../../utils/index.js';
 import type { PolymorphicForwardRefComponent } from '../../utils/index.js';
 import { IconButton } from '../Buttons/IconButton.js';
@@ -166,8 +167,8 @@ export type DateRangePickerProps =
     }
   | {
       enableRangeSelect: true;
-      startDate: Date;
-      endDate: Date;
+      startDate?: Date;
+      endDate?: Date;
       onChange?: (startDate: Date, endDate: Date) => void;
     };
 
@@ -285,6 +286,18 @@ export const DatePicker = React.forwardRef((props, forwardedRef) => {
     ...rest
   } = props;
 
+  const logWarning = useWarningLogger();
+
+  if (process.env.NODE_ENV === 'development') {
+    const onlyOneRangePropPassed =
+      (!!startDate ? 1 : 0) + (!!endDate ? 1 : 0) === 1;
+    if (enableRangeSelect && onlyOneRangePropPassed) {
+      logWarning(
+        '`DatePicker` with `enableRangeSelect` needs *both* `startDate` and `endDate` to either be `Date` or `undefined`. Passing `Date` to just one of them is not allowed.',
+      );
+    }
+  }
+
   const monthNames = localizedNames?.months ?? defaultMonths;
   const shortDays = localizedNames?.shortDays ?? defaultShortDays;
   const longDays = localizedNames?.days ?? defaultLongDays;