Batting first after winning the toss, Pakistan scored 161 for the loss of seven wickets in their allotted 50 overs.
Openers gave Pakistan a steady start with Nain Abidi and Bisma Maroof adding 47 runs for the first wicket.
While Sri Lanka, in its reply, managed only 104 runs with Shashikala Siriwardene making a watchful 58.
Siriwardene batted brilliantly but couldn't manage a partnership as wickets fell at regular intervals.
For Pakistan Qanita Jalil was pick of the bowlers as she took three wickets from in eight overs, while Sana Jalil scalped two.