Not the Nickelodeon film. No, this is the 1973 film which was the last film directed by Nathan H. Juran, helmer of such classics as The 7th Voyage of Sinbad and Attack of the 50 Foot Woman (not to mention a slew of Irwin Allen TV episodes). And yes, it stars Kerwin Mathews (who was the aforementioned Sinbad). Mathews plays a divorced father who saves his son from a werewolf, only to be bitten himself. And truly, hijinks thus ensue. Enjoy.
This film appears to be completely out of print...so enjoy it here while you can.