An inexperienced Sri Lanka upset top-ranked Pakistan with a 64-run victory in their first T20I on Saturday in Lahore.
Eighth-ranked Sri Lanka scored 165-5 before dismissing hosts Pakistan for 101.
Sri Lanka opener Danushka Gunathilaka smashed a career-best 57 off 38 balls after Pakistan captain Sarfaraz Ahmed opted to field after winning the toss, hoping Sri Lanka bowlers would struggle later because of dew.
Recalled Pakistan batsmen Ahmed Shehzad (4) and Umar Akmal (0) failed in their comeback match and the hosts couldn't recover from 22-3 before being bowled out in 17.4 overs.
Sri Lanka were pulled back by 19-year-old Pakistan fast bowler Mohammad Hasnain (3-37), who grabbed a hat trick over separate overs in only his second T20 international.
The second and third T20Is are also at Lahore on Monday and Wednesday respectively.
