diff --git a/packages/catalog-client/src/CatalogClient.ts b/packages/catalog-client/src/CatalogClient.ts
index bd557cfdd2..2bdf63cc49 100644
--- a/packages/catalog-client/src/CatalogClient.ts
+++ b/packages/catalog-client/src/CatalogClient.ts
@@ -20,7 +20,8 @@ import {
   parseEntityRef,
   stringifyLocationRef,
 } from '@backstage/catalog-model';
-import { ResponseError } from '@backstage/errors';
+import { InputError, ResponseError } from '@backstage/errors';
+import { FilterPredicate } from '@backstage/filter-predicates';
 import {
   AddLocationRequest,
   AddLocationResponse,
@@ -47,6 +48,7 @@ import {
   ValidateEntityResponse,
 } from './types/api';
 import {
+  convertFilterToPredicate,
   isQueryEntitiesInitialRequest,
   splitRefsIntoChunks,
   cursorContainsQuery,
@@ -352,11 +354,37 @@ export class CatalogClient implements CatalogApi {
     const body: QueryEntitiesByPredicateRequest = {};
 
     if (isQueryEntitiesInitialRequest(request)) {
-      const { query, limit, offset, orderFields, fullTextFilter, fields } =
-        request;
-      if (query && typeof query === 'object') {
-        body.query = query;
+      const {
+        filter,
+        query,
+        limit,
+        offset,
+        orderFields,
+        fullTextFilter,
+        fields,
+      } = request;
+
+      let filterPredicate: FilterPredicate | undefined;
+      if (query !== undefined) {
+        if (
+          typeof query !== 'object' ||
+          query === null ||
+          Array.isArray(query)
+        ) {
+          throw new InputError('Query must be an object');
+        }
+        filterPredicate = query;
       }
+      if (filter !== undefined) {
+        const converted = convertFilterToPredicate(filter);
+        filterPredicate = filterPredicate
+          ? { $all: [filterPredicate, converted] }
+          : converted;
+      }
+      if (filterPredicate !== undefined) {
+        body.query = filterPredicate as unknown as { [key: string]: any };
+      }
+
       if (limit !== undefined) {
         body.limit = limit;
       }
diff --git a/packages/catalog-client/src/utils.test.ts b/packages/catalog-client/src/utils.test.ts
index 2f00859985..ce60cc3083 100644
--- a/packages/catalog-client/src/utils.test.ts
+++ b/packages/catalog-client/src/utils.test.ts
@@ -14,7 +14,87 @@
  * limitations under the License.
  */
 
-import { splitRefsIntoChunks } from './utils';
+import { CATALOG_FILTER_EXISTS } from './types/api';
+import { convertFilterToPredicate, splitRefsIntoChunks } from './utils';
+
+describe('convertFilterToPredicate', () => {
+  it('converts a single string value', () => {
+    expect(convertFilterToPredicate({ kind: 'component' })).toEqual({
+      kind: 'component',
+    });
+  });
+
+  it('converts multiple keys into $all', () => {
+    expect(
+      convertFilterToPredicate({
+        kind: 'component',
+        'spec.type': 'service',
+      }),
+    ).toEqual({
+      $all: [{ kind: 'component' }, { 'spec.type': 'service' }],
+    });
+  });
+
+  it('converts an array of string values into $in', () => {
+    expect(
+      convertFilterToPredicate({ 'spec.type': ['service', 'website'] }),
+    ).toEqual({
+      'spec.type': { $in: ['service', 'website'] },
+    });
+  });
+
+  it('converts CATALOG_FILTER_EXISTS into $exists', () => {
+    expect(
+      convertFilterToPredicate({ 'spec.owner': CATALOG_FILTER_EXISTS }),
+    ).toEqual({
+      'spec.owner': { $exists: true },
+    });
+  });
+
+  it('converts an array of records into $any (OR)', () => {
+    expect(
+      convertFilterToPredicate([{ kind: 'component' }, { kind: 'api' }]),
+    ).toEqual({
+      $any: [{ kind: 'component' }, { kind: 'api' }],
+    });
+  });
+
+  it('converts array of records with multiple keys each', () => {
+    expect(
+      convertFilterToPredicate([
+        { kind: 'component', 'spec.type': 'service' },
+        { kind: 'api' },
+      ]),
+    ).toEqual({
+      $any: [
+        { $all: [{ kind: 'component' }, { 'spec.type': 'service' }] },
+        { kind: 'api' },
+      ],
+    });
+  });
+
+  it('treats CATALOG_FILTER_EXISTS mixed with string values as just existence', () => {
+    expect(
+      convertFilterToPredicate({
+        'spec.owner': [CATALOG_FILTER_EXISTS, 'team-a'],
+      }),
+    ).toEqual({
+      'spec.owner': { $exists: true },
+    });
+  });
+
+  it('converts a single-element array filter without wrapping in $any', () => {
+    expect(convertFilterToPredicate([{ kind: 'component' }])).toEqual({
+      kind: 'component',
+    });
+  });
+
+  it('ignores entries with no valid values', () => {
+    expect(
+      convertFilterToPredicate({ kind: 'component', other: [] as string[] }),
+    ).toEqual({ kind: 'component' });
+  });
+});
 
 describe('splitRefsIntoChunks', () => {
   it('splits by count limit', () => {
diff --git a/packages/catalog-client/src/utils.ts b/packages/catalog-client/src/utils.ts
index fc867d8670..231aa2409f 100644
--- a/packages/catalog-client/src/utils.ts
+++ b/packages/catalog-client/src/utils.ts
@@ -14,7 +14,13 @@
  * limitations under the License.
  */
 
+import type {
+  FilterPredicate,
+  FilterPredicateExpression,
+} from '@backstage/filter-predicates';
 import {
+  CATALOG_FILTER_EXISTS,
+  EntityFilterQuery,
   QueryEntitiesCursorRequest,
   QueryEntitiesInitialRequest,
   QueryEntitiesRequest,
@@ -39,6 +45,45 @@ export function cursorContainsQuery(cursor: string): boolean {
   }
 }
 
+/**
+ * Converts an {@link EntityFilterQuery} into a predicate query object.
+ * @internal
+ */
+export function convertFilterToPredicate(filter: EntityFilterQuery):
+  | FilterPredicateExpression
+  | {
+      $all: FilterPredicate[];
+    }
+  | {
+      $any: FilterPredicate[];
+    } {
+  const records = [filter].flat();
+
+  const clauses = records.map(record => {
+    const parts: FilterPredicateExpression[] = [];
+
+    for (const [key, value] of Object.entries(record)) {
+      const values = [value].flat();
+      const strings = values.filter((v): v is string => typeof v === 'string');
+      const hasExists = values.some(v => v === CATALOG_FILTER_EXISTS);
+
+      if (hasExists) {
+        // Ignore whether there ALSO were some strings - that would boil down to
+        // just existence anyway since there's effectively an OR between them
+        parts.push({ [key]: { $exists: true } } as FilterPredicateExpression);
+      } else if (strings.length === 1) {
+        parts.push({ [key]: strings[0] } as FilterPredicateExpression);
+      } else if (strings.length > 1) {
+        parts.push({ [key]: { $in: strings } } as FilterPredicateExpression);
+      }
+    }
+
+    return parts.length === 1 ? parts[0] : { $all: parts };
+  });
+
+  return clauses.length === 1 ? clauses[0] : { $any: clauses };
+}
+
 /**
  * Takes a set of entity refs, and splits them into chunks (groups) such that
  * the total string length in each chunk does not exceed the default Express.js