diff --git a/src/spikeinterface/sorters/external/kilosort4.py b/src/spikeinterface/sorters/external/kilosort4.py
index a7f40a9558..84bab9447a 100644
--- a/src/spikeinterface/sorters/external/kilosort4.py
+++ b/src/spikeinterface/sorters/external/kilosort4.py
@@ -1,9 +1,12 @@
 from __future__ import annotations
 
 from pathlib import Path
+import random
 from typing import Union
 from packaging import version
 
+from spikeinterface.core.generate import _ensure_seed
+
 from ..basesorter import BaseSorter
 from .kilosortbase import KilosortBase
 
@@ -57,6 +60,7 @@ class Kilosort4Sorter(BaseSorter):
         "skip_kilosort_preprocessing": False,
         "scaleproc": None,
         "torch_device": "auto",
+        "seed": None,
     }
 
     _params_description = {
@@ -99,6 +103,7 @@ class Kilosort4Sorter(BaseSorter):
         "skip_kilosort_preprocessing": "Can optionally skip the internal kilosort preprocessing",
         "scaleproc": "int16 scaling of whitened data, if None set to 200.",
         "torch_device": "Select the torch device auto/cuda/cpu",
+        "seed": "Kilosort random seed",
     }
 
     sorter_description = """Kilosort4 is a Python package for spike sorting on GPUs with template matching.
@@ -244,9 +249,11 @@ def _run_from_folder(cls, sorter_output_folder, params, verbose):
             ops["Wrot"] = torch.as_tensor(np.eye(recording.get_num_channels()))
             ops["Nbatches"] = bfile.n_batches
 
-        np.random.seed(1)
-        torch.cuda.manual_seed_all(1)
-        torch.random.manual_seed(1)
+        params["seed"] = _ensure_seed(params["seed"])
+        random.seed(params["seed"])
+        np.random.seed(params["seed"])
+        torch.cuda.manual_seed_all(params["seed"])
+        torch.random.manual_seed(params["seed"])
         # if not params["skip_kilosort_preprocessing"]:
         if not params["do_correction"]:
             print("Skipping drift correction.")
diff --git a/src/spikeinterface/sorters/external/mountainsort5.py b/src/spikeinterface/sorters/external/mountainsort5.py
index cf6933c9e6..aea5056933 100644
--- a/src/spikeinterface/sorters/external/mountainsort5.py
+++ b/src/spikeinterface/sorters/external/mountainsort5.py
@@ -1,12 +1,14 @@
 from __future__ import annotations
 
 from pathlib import Path
+import random
 from packaging.version import parse
 
 import shutil
 import numpy as np
 from warnings import warn
 
+from spikeinterface.core.generate import _ensure_seed
 from spikeinterface.preprocessing import bandpass_filter, whiten
 
 from spikeinterface.core.baserecording import BaseRecording
@@ -45,6 +47,7 @@ class Mountainsort5Sorter(BaseSorter):
         "filter": True,
         "whiten": True,  # Important to do whitening
         "delete_temporary_recording": True,
+        "seed": None,
     }
 
     _params_description = {
@@ -69,6 +72,7 @@ class Mountainsort5Sorter(BaseSorter):
         "filter": "Enable or disable filter",
         "whiten": "Enable or disable whitening",
         "delete_temporary_recording": "If True, the temporary recording file is deleted after sorting (this may fail on Windows requiring the end-user to delete the file themselves later)",
+        "seed": "Random seed",
     }
 
     sorter_description = "MountainSort5 uses Isosplit clustering. It is an updated version of MountainSort4. See https://doi.org/10.1016/j.neuron.2017.08.030"
@@ -184,6 +188,10 @@ def _run_from_folder(cls, sorter_output_folder, params, verbose):
             block_sorting_parameters=scheme2_sorting_parameters, block_duration_sec=p["scheme3_block_duration_sec"]
         )
 
+        params["seed"] = _ensure_seed(params["seed"])
+        random.seed(params["seed"])
+        np.random.seed(params["seed"])
+
         if not recording.is_binary_compatible():
             recording_cached = recording.save(folder=sorter_output_folder / "recording", **get_job_kwargs(p, verbose))
         else: