Hampshire's T20 captain, having played in New Zealand’s HRV Cup and Australia's Big Bash within the last month, helped defeat the Chittagong Kings by six wickets at the Sheikh Abu Naser Stadium, Khulna.
He helped restrict Chittagong to 132-5 after Rangpur had lost the toss, trapping Surrey's Jason Roy lbw on his way to figures of 4-0-26-1, after taking the new ball with West Indies star Fidel Edwards.
Mascarenhas then helped see his new teammates - who include Kevin and Niall O'Brien - to their target with three balls to spare, hitting an unbeaten six against a Chittagong attack including Jacob Oram, Shaun Tait and Ravi Bopara.
Meanwhile Sean Ervine, who is playing for Duronto Rajshahi as he did last year, lost to Dhaka Gladiators by 13 runs, despite an unbeaten 33 from Simon Katich.
The Hampshire all-rounder was not required to bat or bowl.