The Shaheens had dominated the two rain affected four-day matches before heading into the one-day series.
On Thursday, all-rounder Mohammad Abbas Afridi starred for the Shaheens with a four-wicket haul which enabled the Shaheens to send the hosts packing for a paltry 102 after winning the toss and electing to field first.
Omair Bin Yousuf scored 38 off 57 balls (six fours) as the Shaheens overhauled the target for the loss of four wickets in 21.2 overs. Mohammad Taha scored an unbeaten 19 off 10 balls (four fours) and added 27 runs for the unfinished fifth-wicket stand with Salman Ali Agha (12 not out) to ensure a comprehensive win for the Shaheens and a one-zero lead in the series.
Earlier, Sri Lanka A were rolled over for 102 in 32.2 overs. Pakistan pace bowlers Abbas Afridi, Khurram Shahzad and Naseem Shah bowled with sustained hostility, pace and accuracy as the hosts were sent packing inside 32.2 overs.
Abbas took four wickets for 30 runs in his 10 overs, Khurram grabbed three wickets for 19 in 7.2 overs while Naseem finished his 10 overs with two wickets for 26 runs.
Captain and opener Kamindu Mendis top-scored with 34 off 51 balls, Sahan Arachchinge contributed 23 runs. The second match of the series will be played at the same venue on Saturday, with the third and final match on Monday.
Scores in Brief:
Pakistan Shaheens beat Sri Lanka A by six wickets
Sri Lanka A 102 all out, 32.2 overs (Kamindu Mendis 34, Sahan Arachchinge 23; Abbas Afridi 4-30, Khurram Shahzad 3-19, Naseem Shah 2-26)
Pakistan Shaheens 103 for 4, 21.2 overs (Omair Bin Yousuf 38, Ashian Daniel 2-30)