Chasing a modest 148-run target, Pakistan were on course for victory with Haris Sohail’s 50-ball 52 with four boundaries and a six but leg-spinner Wanindu Hasaranga turned the tables with 3-21 to restrict Pakistan to 134-6 in 20 overs.
Hasaranga had Sohail stumped in the 16th over and then dismissed Pakistan skipper Sarfaraz Ahmed (16-ball 17) in the 18th to give Sri Lanka victory on a match day designated as Pink Day for breast cancer awareness.
Oshada Fernando struck a brilliant 48-ball 78 with three sixes and eight boundaries -- the highest by a Sri Lankan player on T20I debut -- to lift Sri Lanka to 147-7 in their 20 overs.
Jehan Mubarak and Danushka Gunathilaka -- who both scored 46 each -- had held the previous record for most runs on Twenty20 debut for Sri Lanka.
Sri Lanka’s victory -- their first-ever Twenty20 series whitewash -- was achieved despite missing ten of their top players, including regular Twenty20 skipper Lasith Malinga, who refused to tour Pakistan over security fears.
But that did not hurt Sri Lanka as they staged a remarkable comeback after losing the one-day series 2-0 by winning the first two matches of the T20 series by 64 and 35 runs respectively.
Before this, Pakistan’s only Twenty20 whitewash was at the hands of England in United Arab Emirates in 2015.
Pakistan’s start was once again disastrous as they lost aggressive opener Fakhar Zaman off the first ball of their innings, bowled by Kasun Rajitha for nought.
Babar Azam (32-ball 27) and Sohail added 76 for the second wicket but Sri Lanka applied the brakes as boundaries dried up.