St Just won the Vinter Cup on Tuesday for the 14th time in 16 years by beating Penzance by five wickets off the last ball of the match.
Needing 140 for victory, St Just required five off the last two balls and Gary Thomas hit a boundary and then scrambled a single.
Man-of-the-match Gareth May earlier hit 52 for St Just, after Christian Purchase's 64 in Penzance's 139-5.
St Just will now play Grampound Road in the WT Edwards Cup final.
The WT Edwards Cup match between the winners of west Cornwall's Vinter Cup and east Cornwall's Hawkey Cup will be played at St Austell on Wednesday, 20 July.