diff --git a/trackpy/linking/linking.py b/trackpy/linking/linking.py
index 5b9e111e..da67f4e6 100644
--- a/trackpy/linking/linking.py
+++ b/trackpy/linking/linking.py
@@ -5,6 +5,8 @@
 import warnings
 import logging
 import itertools, functools
+from concurrent import futures
+from multiprocessing import cpu_count
 
 import numpy as np
 
@@ -499,12 +501,19 @@ def next_level(self, coords, t, extra_data=None):
 
     def assign_links(self):
         spl, dpl = [], []
-        for source_set, dest_set in self.subnets:
+
+        def link_subnet(subnet_sets):
+            source_set, dest_set = subnet_sets
             for sp in source_set:
                 sp.forward_cands.sort(key=lambda x: x[1])
 
-            sn_spl, sn_dpl = self.subnet_linker(source_set, dest_set,
-                                                self.search_range)
+            return self.subnet_linker(source_set, dest_set,
+                                      self.search_range)
+
+        workers = futures.ThreadPoolExecutor(max_workers=cpu_count())
+        futs = [workers.submit(link_subnet, sub) for sub in self.subnets]
+        for fut in futures.as_completed(futs):
+            sn_spl, sn_dpl = fut.result()
             spl.extend(sn_spl)
             dpl.extend(sn_dpl)
 
diff --git a/trackpy/linking/subnetlinker.py b/trackpy/linking/subnetlinker.py
index 1753e2f1..ce7d9f56 100644
--- a/trackpy/linking/subnetlinker.py
+++ b/trackpy/linking/subnetlinker.py
@@ -238,7 +238,7 @@ def numba_link(s_sn, dest_size, search_range, max_size=30, diag=False):
     dest_results = [dcands[i] if i >= 0 else None for i in best_assignments]
     return source_results, dest_results
 
-@try_numba_jit(nopython=True)
+@try_numba_jit(nopython=True, nogil=True)
 def _numba_subnet_norecur(ncands, candsarray, dists2array, cur_assignments,
                           cur_sums, tmp_assignments, best_assignments):
     """Find the optimal track assignments for a subnetwork, without recursion.