diff --git a/src/apify_client/_resource_clients/_resource_client.py b/src/apify_client/_resource_clients/_resource_client.py
index bb5d85fd..4be84764 100644
--- a/src/apify_client/_resource_clients/_resource_client.py
+++ b/src/apify_client/_resource_clients/_resource_client.py
@@ -18,7 +18,7 @@
 if TYPE_CHECKING:
     from apify_client._client_registry import ClientRegistry, ClientRegistryAsync
     from apify_client.http_clients import HttpClient, HttpClientAsync
-    from apify_client.types import Timeout
+    from apify_client.types import QueryParams, QueryParamValue, Timeout
 
 _TerminalActorJobStatus = Literal['SUCCEEDED', 'FAILED', 'TIMED-OUT', 'ABORTED']
 """Subset of `ActorJobStatus` values that indicate the job has finished and will not change again."""
@@ -41,7 +41,7 @@ def __init__(
         resource_path: str,
         client_registry: Any,
         resource_id: str | None = None,
-        params: dict | None = None,
+        params: QueryParams | None = None,
         api_base_url: str | None = None,
     ) -> None:
         """Initialize the resource client.
@@ -63,7 +63,7 @@ def __init__(
         self._api_base_url = api_base_url or base_url
         self._public_base_url = public_base_url
         self._http_client = http_client
-        self._default_params = params or {}
+        self._default_params = dict(params) if params else {}
         self._resource_path = resource_path
         self._resource_id = resource_id
         self._client_registry = client_registry
@@ -120,7 +120,7 @@ def _build_url(
 
         return url
 
-    def _build_public_url(self, path: str, params: dict[str, Any]) -> str:
+    def _build_public_url(self, path: str, params: QueryParams) -> str:
         """Build a public resource URL with API-normalized query params.
 
         Normalizes `params` the same way the HTTP request path does (bool -> true/false, list -> comma-joined,
@@ -139,7 +139,7 @@ def _build_public_url(self, path: str, params: dict[str, Any]) -> str:
             public_url = public_url._replace(query=urlencode(filtered_params))
         return urlunparse(public_url)
 
-    def _build_params(self, **kwargs: Any) -> dict:
+    def _build_params(self, **kwargs: QueryParamValue) -> dict[str, QueryParamValue]:
         """Merge default params with method params, filtering out None values.
 
         Args:
@@ -200,7 +200,7 @@ def __init__(
         resource_path: str,
         client_registry: ClientRegistry,
         resource_id: str | None = None,
-        params: dict | None = None,
+        params: QueryParams | None = None,
         api_base_url: str | None = None,
     ) -> None:
         """Initialize the resource client.
@@ -313,7 +313,7 @@ def _wait_for_finish(
         self,
         *,
         url: str,
-        params: dict,
+        params: QueryParams,
         timeout: Timeout,
         wait_duration: timedelta | None = None,
     ) -> dict | None:
@@ -395,7 +395,7 @@ def __init__(
         resource_path: str,
         client_registry: ClientRegistryAsync,
         resource_id: str | None = None,
-        params: dict | None = None,
+        params: QueryParams | None = None,
         api_base_url: str | None = None,
     ) -> None:
         """Initialize the resource client.
@@ -508,7 +508,7 @@ async def _wait_for_finish(
         self,
         *,
         url: str,
-        params: dict,
+        params: QueryParams,
         timeout: Timeout,
         wait_duration: timedelta | None = None,
     ) -> dict | None:
diff --git a/src/apify_client/_resource_clients/request_queue.py b/src/apify_client/_resource_clients/request_queue.py
index 0540bb35..baa1bf30 100644
--- a/src/apify_client/_resource_clients/request_queue.py
+++ b/src/apify_client/_resource_clients/request_queue.py
@@ -56,7 +56,7 @@
         RequestWithoutIdCamelDict,
         RequestWithoutIdDict,
     )
-    from apify_client.types import Timeout
+    from apify_client.types import QueryParams, Timeout
 
 _RQ_MAX_REQUESTS_PER_BATCH = 25
 """Maximum number of requests the API accepts in a single batch call."""
@@ -946,7 +946,7 @@ async def _batch_add_requests_worker(
         self,
         *,
         queue: asyncio.Queue[Iterable[bytes]],
-        request_params: dict,
+        request_params: QueryParams,
         timeout: Timeout,
     ) -> BatchAddResponse:
         """Worker function to process a batch of requests.
diff --git a/src/apify_client/http_clients/_base.py b/src/apify_client/http_clients/_base.py
index b06d542c..cad2efdc 100644
--- a/src/apify_client/http_clients/_base.py
+++ b/src/apify_client/http_clients/_base.py
@@ -43,7 +43,7 @@
     from typing import Self
 
     from apify_client.http_compressors._base import HttpCompressor
-    from apify_client.types import JsonSerializable, StreamedBodySource, Timeout
+    from apify_client.types import JsonSerializable, QueryParams, StreamedBodySource, Timeout
 
 logger = logging.getLogger(logger_name)
 logger_once = LoggerOnce(logger)
@@ -227,7 +227,7 @@ def _get_header(headers: dict[str, str], name: str) -> str | None:
         return next((value for key, value in headers.items() if key.lower() == name.lower()), None)
 
     @staticmethod
-    def _parse_params(params: dict[str, Any] | None) -> dict[str, Any] | None:
+    def _parse_params(params: QueryParams | None) -> dict[str, Any] | None:
         """Convert request parameters to Apify API-compatible formats.
 
         Converts booleans to 'false'/'true', lists to comma-separated strings, datetimes to ISO 8601 Zulu format.
@@ -309,7 +309,7 @@ def _prepare_request_call(
         self,
         *,
         headers: dict[str, str] | None = None,
-        params: dict[str, Any] | None = None,
+        params: QueryParams | None = None,
         data: str | bytes | bytearray | StreamedBodySource | None = None,
         json: JsonSerializable | None = None,
     ) -> tuple[dict[str, str], dict[str, Any] | None, bytes | StreamedRequestBody | None]:
@@ -504,7 +504,7 @@ def call(
         method: str,
         url: str,
         headers: dict[str, str] | None = None,
-        params: dict[str, Any] | None = None,
+        params: QueryParams | None = None,
         data: str | bytes | bytearray | StreamedBodySource | None = None,
         json: JsonSerializable | None = None,
         stream: bool | None = None,
@@ -516,7 +516,8 @@ def call(
             method: HTTP method (GET, POST, PUT, DELETE, etc.).
             url: Full URL to make the request to.
             headers: Additional headers to include.
-            params: Query parameters to append to the URL.
+            params: Query parameters to append to the URL. See `QueryParamValue` for how each value is converted
+                before it is sent.
             data: Raw request body. An `io.IOBase` stream such as an open file, an iterable of byte chunks, or a
                 streamed `HttpResponse` is sent in chunks as it is read, and any other object with a callable `read`
                 is read whole, see `StreamedRequestBody`. Streaming is experimental, and its behavior may change in
@@ -715,7 +716,7 @@ async def call(
         method: str,
         url: str,
         headers: dict[str, str] | None = None,
-        params: dict[str, Any] | None = None,
+        params: QueryParams | None = None,
         data: str | bytes | bytearray | StreamedBodySource | None = None,
         json: JsonSerializable | None = None,
         stream: bool | None = None,
@@ -727,7 +728,8 @@ async def call(
             method: HTTP method (GET, POST, PUT, DELETE, etc.).
             url: Full URL to make the request to.
             headers: Additional headers to include.
-            params: Query parameters to append to the URL.
+            params: Query parameters to append to the URL. See `QueryParamValue` for how each value is converted
+                before it is sent.
             data: Raw request body. An `io.IOBase` stream such as an open file, an iterable of byte chunks, or a
                 streamed `HttpResponse` is sent in chunks as it is read, and any other object with a callable `read`
                 is read whole, see `StreamedRequestBody`. Streaming is experimental, and its behavior may change in
diff --git a/src/apify_client/types.py b/src/apify_client/types.py
index f7a8d555..d7eb30d3 100644
--- a/src/apify_client/types.py
+++ b/src/apify_client/types.py
@@ -1,7 +1,8 @@
 from __future__ import annotations
 
 from collections.abc import AsyncIterable, Iterable, Mapping, Sequence
-from datetime import timedelta
+from datetime import datetime, timedelta
+from decimal import Decimal
 from typing import IO, TYPE_CHECKING, Literal, Protocol
 
 from apify_client._models import CreateWebhookRequest, WebhookRepresentation
@@ -19,6 +20,18 @@
 HttpCompressionAlgorithm = Literal['brotli', 'gzip']
 """Accepted string literals for the `compression` parameter on `ApifyClient` and `ApifyClientAsync`."""
 
+QueryParamValue = str | int | float | bool | Decimal | datetime | list[str] | None
+"""Type of one query parameter value accepted by the client.
+
+The HTTP client converts a value before sending it: a `bool` becomes `true` or `false`, a `list[str]` becomes one
+comma-separated value, a `datetime` becomes an ISO 8601 string in UTC (a naive one is treated as UTC), and a `None`
+value is left out. Any other value is sent as its `str()`. Only a `list` is joined, so pass a `list`, not a tuple
+or another sequence.
+"""
+
+QueryParams = Mapping[str, QueryParamValue]
+"""Type for the `params` parameter on `HttpClient.call` and `HttpClientAsync.call`: query parameters of the request."""
+
 Timeout = timedelta | Literal['no_timeout', 'short', 'medium', 'long']
 """Type for the `timeout` parameter on resource client methods.
 
@@ -91,6 +104,8 @@ def read(self) -> bytes | str | Awaitable[bytes | str]:
 __all__ = [
     'HttpCompressionAlgorithm',
     'JsonSerializable',
+    'QueryParamValue',
+    'QueryParams',
     'StreamedBodySource',
     'SupportsRead',
     'Timeout',
diff --git a/tests/unit/test_pluggable_http_client.py b/tests/unit/test_pluggable_http_client.py
index edbc6c0a..2034b832 100644
--- a/tests/unit/test_pluggable_http_client.py
+++ b/tests/unit/test_pluggable_http_client.py
@@ -35,7 +35,7 @@
 
     from pytest_httpserver import HTTPServer
 
-    from apify_client.types import StreamedBodySource, Timeout
+    from apify_client.types import QueryParams, StreamedBodySource, Timeout
 
 
 @dataclass
@@ -94,7 +94,7 @@ def call(
         method: str,
         url: str,
         headers: dict[str, str] | None = None,
-        params: dict[str, Any] | None = None,
+        params: QueryParams | None = None,
         data: str | bytes | bytearray | StreamedBodySource | None = None,
         json: Any = None,
         stream: bool | None = None,
@@ -128,7 +128,7 @@ async def call(
         method: str,
         url: str,
         headers: dict[str, str] | None = None,
-        params: dict[str, Any] | None = None,
+        params: QueryParams | None = None,
         data: str | bytes | bytearray | StreamedBodySource | None = None,
         json: Any = None,
         stream: bool | None = None,
@@ -550,7 +550,7 @@ def call(
         method: str,
         url: str,
         headers: dict[str, str] | None = None,
-        params: dict[str, Any] | None = None,
+        params: QueryParams | None = None,
         data: str | bytes | bytearray | StreamedBodySource | None = None,
         json: Any = None,
         **_kwargs: Any,
@@ -575,7 +575,7 @@ async def call(
         method: str,
         url: str,
         headers: dict[str, str] | None = None,
-        params: dict[str, Any] | None = None,
+        params: QueryParams | None = None,
         data: str | bytes | bytearray | StreamedBodySource | None = None,
         json: Any = None,
         **_kwargs: Any,