Callington beat Newquay by just seven runs to lift the Hawkey Cup for the first time since 2001.
They set a total of 131 from their 20 overs at St Austell, with skipper Aidan Libby top-scoring with 46 not out.
In reply, Newquay started shakily but Adam Cocking hit 56 not out to set up a tense finish, though they fell short in the final over.
It capped a memorable day for the Libby family as brother Jake returned to professional cricket after injury.
He made 123 on his comeback for Nottinghamshire's second XI against Derbyshire, after suffering knee ligament damage in January.