Jayawardene's team beat the home side by a whopping 234 runs in the third and final day-night international -- the heaviest one-day defeat suffered by Pakistan.
Sri Lanka piled up a mammoth 309-5 in their 50 overs thanks to a career-best 137 from opener Tillakaratne Dilshan and Kumar Sangakkara's 50.
Pacemen Nuwan Kulasekara (3-17) and Thilan Thushara (3-33) then dismissed Pakistan for a mere 75 in 22.5 overs -- the lowest total at home by Shoaib Malik's team in all one-day cricket.
Jayawardene was delighted that his side had staged a comeback after losing the first match by eight wickets in Karachi on Tuesday.
Sri Lanka won the second game by 129 runs -- also played in Karachi.
"This is our sixth win in seven one-day series and the only one which hurt badly was our defeat against India at home (last year) and hopefully we turn things around this time," Jayawardene said.
Sri Lanka take on India in the first of five one-day matches in Colombo on January 28.
They will also