diff --git a/homeassistant/package_constraints.txt b/homeassistant/package_constraints.txt
index 165bd547dae..b26cd30f0d6 100644
--- a/homeassistant/package_constraints.txt
+++ b/homeassistant/package_constraints.txt
@@ -215,3 +215,8 @@ rpds-py==0.26.0
 
 # Constraint num2words to 0.5.14 as 0.5.15 and 0.5.16 were removed from PyPI
 num2words==0.5.14
+
+# pymodbus does not follow SemVer, and it keeps getting
+# downgraded or upgraded by custom components
+# This ensures all use the same version
+pymodbus==3.11.1
diff --git a/script/gen_requirements_all.py b/script/gen_requirements_all.py
index a62f2f62bc1..b710fbc31ed 100755
--- a/script/gen_requirements_all.py
+++ b/script/gen_requirements_all.py
@@ -241,6 +241,11 @@ rpds-py==0.26.0
 
 # Constraint num2words to 0.5.14 as 0.5.15 and 0.5.16 were removed from PyPI
 num2words==0.5.14
+
+# pymodbus does not follow SemVer, and it keeps getting
+# downgraded or upgraded by custom components
+# This ensures all use the same version
+pymodbus==3.11.1
 """
 
 GENERATED_MESSAGE = (