Misbah-ul-Haq scored 66 and BMAJ Mendis took three wickets. Pakistan overhauled the victory target in 47.2 overs for the loss of 7 wickets.
Earlier Sri Lanka set Pakistan a target of 219 to clinch the 5th one-day international.
KC Sangakkara top-scored for Sri Lanka with 78 as the tourists made 218-9 after winning the toss. Sohail Tanvir with 4-34 was Pakistan’s most impressive bowler.