The port city team looked set to win the game but two match defining performances from Anamul and Afghan recruit Janat denied them as Barishal raced to 171-7 with four balls to spare.
Anamul’s attacking knock gave the Barishal innings momentum early on as he and Saif Hasan added 48-run for the opening stand in which Saif's contribution was just 10.
After Mehedi Hasan Rana broke through with the wicket of Saif, Chattogram’s left-arm spinner Nihaduzzaman made Chattogram the front runners in the contest with his career-best returns of 4-17.
Nihaduzzaman took the key scalp of Shakib Al Hasan (two) and Mahmudullah (0) in consecutive deliveries before getting rid of Chaturanga de Silva (three).
But Anamul was unfazed by the loss of wickets at the other end as he kept smashing the ball at all corners of the ground in an innings where he hit six fours and as many sixes.
Anamul’s knock came to an end when pacer Mrittunjoy Chowdhury rattled his stumps, reducing Barishal to 113-5.
Soon after that Nihaduzzaman claimed his fourth wicket of the game, dismissing the inform Iftikhar Ahmed for 13, tilting the game toward Chattogram.
However, Janat refused to give up as he unleashed some powerful shots around the wicket and shared a partnership with Salman Hossain worth 50 runs off 21 balls to again put Barishal in the driver’s seat.
With the scores level, Rana removed Janat, who struck three fours and two towering sixes in his brief stay.
New batter Mohammad Wasim hit a boundary in the first ball he faced to take the side home. Salman was unbeaten on 18 off 14 after smashing two fours and one six.
Earlier, Barishal pacers Khaled Ahmed and Kamrul Islam took two wickets each while pacer Mohammad Wasim played a vital role in strangling the Chattogram innings, with his 1-22 in four overs.
However, Afif Hossain struck 37 off 23 and Curtis Campher hit an unbeaten 25-ball 45 to help Chattogram post a challenging total.
The Shakib led side now has 12 points from eight matches following the victory.
Mashrafe Bin Mortaza led Sylhet Strikers also have the same points but they moved down to second spot for the first time based on the net run rate after suffering a six-wicket defeat to Rangpur earlier on Friday.