Pathum Nissanka scores his second century in three games to lead Sri Lanka to a dominant seven-wicket victory.
Avishka Fernando provides early momentum with a belligerent 66-ball 91.
Sri Lanka chase down a target of 267 in just 35.2 overs.
Afghanistan collapse from 143/2 to 266 all out, losing their last six wickets for 43 runs.
Rahmat Shah and Azmatullah Omarzai score fifties for Afghanistan, but fail to build on promising starts.
Pramod Madushan takes 3 for 45 for Sri Lanka, while Dunith Wellalage and Akila Dananjaya impress with two wickets each.
Sri Lanka win the series 3-0, with Nissanka finishing as the highest run-scorer with 346 runs.
Afghanistan will be disappointed with their batting performance throughout the series.
Sri Lanka will be happy with their clinical performance and will look to build on this momentum in the future.
This was a convincing win for Sri Lanka, who dominated Afghanistan from start to finish.