diff --git a/netbox/dcim/forms/filtersets.py b/netbox/dcim/forms/filtersets.py
index 41d426e8627..9728a1135b3 100644
--- a/netbox/dcim/forms/filtersets.py
+++ b/netbox/dcim/forms/filtersets.py
@@ -1435,7 +1435,7 @@ class InterfaceFilterForm(PathEndpointFilterForm, DeviceComponentFilterForm):
     tx_power = forms.IntegerField(
         required=False,
         label=_('Transmit power (dBm)'),
-        min_value=0,
+        min_value=-127,
         max_value=127
     )
     vrf_id = DynamicModelMultipleChoiceField(
diff --git a/netbox/dcim/migrations/0201_alter_interface_tx_power.py b/netbox/dcim/migrations/0201_alter_interface_tx_power.py
new file mode 100644
index 00000000000..c626f5731f0
--- /dev/null
+++ b/netbox/dcim/migrations/0201_alter_interface_tx_power.py
@@ -0,0 +1,21 @@
+# Generated by Django 5.1.8 on 2025-04-17 03:36
+
+import django.core.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('dcim', '0200_populate_mac_addresses'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='interface',
+            name='tx_power',
+            field=models.SmallIntegerField(blank=True, null=True, validators=[
+                django.core.validators.MinValueValidator(-127), django.core.validators.MaxValueValidator(127)
+            ]),
+        ),
+    ]
diff --git a/netbox/dcim/models/device_components.py b/netbox/dcim/models/device_components.py
index 632121dc2e6..50228058ce1 100644
--- a/netbox/dcim/models/device_components.py
+++ b/netbox/dcim/models/device_components.py
@@ -710,10 +710,13 @@ class Interface(ModularComponentModel, BaseInterface, CabledObjectModel, PathEnd
         verbose_name=('channel width (MHz)'),
         help_text=_("Populated by selected channel (if set)")
     )
-    tx_power = models.PositiveSmallIntegerField(
+    tx_power = models.SmallIntegerField(
         blank=True,
         null=True,
-        validators=(MaxValueValidator(127),),
+        validators=[
+            MinValueValidator(-127),
+            MaxValueValidator(127)
+        ],
         verbose_name=_('transmit power (dBm)')
     )
     poe_mode = models.CharField(
diff --git a/netbox/dcim/tests/test_api.py b/netbox/dcim/tests/test_api.py
index b1ed4aca33f..ccbdcee16c5 100644
--- a/netbox/dcim/tests/test_api.py
+++ b/netbox/dcim/tests/test_api.py
@@ -1743,7 +1743,7 @@ def setUpTestData(cls):
                 'name': 'Interface 8',
                 'type': InterfaceTypeChoices.TYPE_80211A,
                 'mode': InterfaceModeChoices.MODE_Q_IN_Q,
-                'tx_power': 10,
+                'tx_power': -10,
                 'wireless_lans': [wireless_lans[0].pk, wireless_lans[1].pk],
                 'rf_channel': "",
                 'qinq_svlan': vlans[3].pk,
diff --git a/netbox/dcim/tests/test_filtersets.py b/netbox/dcim/tests/test_filtersets.py
index 727389ef1bf..cc877733c41 100644
--- a/netbox/dcim/tests/test_filtersets.py
+++ b/netbox/dcim/tests/test_filtersets.py
@@ -4072,7 +4072,7 @@ def setUpTestData(cls):
                 type=InterfaceTypeChoices.TYPE_OTHER,
                 enabled=False,
                 mgmt_only=False,
-                tx_power=40,
+                tx_power=-40,
                 mode=InterfaceModeChoices.MODE_Q_IN_Q,
                 qinq_svlan=vlans[2]
             ),
@@ -4340,7 +4340,10 @@ def test_rf_channel_width(self):
 
     def test_tx_power(self):
         params = {'tx_power': [40]}
-        self.assertEqual(self.filterset(params, self.queryset).qs.count(), 3)
+        self.assertEqual(self.filterset(params, self.queryset).qs.count(), 2)
+
+        params = {'tx_power': [-40]}
+        self.assertEqual(self.filterset(params, self.queryset).qs.count(), 1)
 
     def test_vrf(self):
         vrfs = VRF.objects.all()[:2]
diff --git a/netbox/dcim/tests/test_views.py b/netbox/dcim/tests/test_views.py
index b8421788291..068be6df975 100644
--- a/netbox/dcim/tests/test_views.py
+++ b/netbox/dcim/tests/test_views.py
@@ -2660,7 +2660,7 @@ def setUpTestData(cls):
             'poe_mode': InterfacePoEModeChoices.MODE_PD,
             'poe_type': InterfacePoETypeChoices.TYPE_2_8023AT,
             'mode': InterfaceModeChoices.MODE_TAGGED,
-            'tx_power': 10,
+            'tx_power': -10,
             'untagged_vlan': vlans[0].pk,
             'tagged_vlans': [v.pk for v in vlans[1:4]],
             'vrf': vrfs[1].pk,