Charith Asalanka was named as deputy to both Hasaranga and Mendis, Sri Lanka Cricket (SLC) said in a statement.
Hasaranga will make his comeback after missing the Asia Cup and the 50-overs World Cup earlier this year after picking up an injury in the Lanka Premier League in August.
He succeeds regular skipper Dasun Shanaka who was named in their preliminary squads for three ODIs and as many T20 matches against the African side on home soil starting January 6th.
Mendis took over ODI captaincy two games into the World Cup in India after Shanaka was ruled out of the tournament due to a thigh injury.
Sri Lanka had a disappointing tournament, finishing ninth out of 10 teams with two wins from nine games.
The SLC had responded by naming a new selection committee led by former opener Upul Tharanga that also includes former player Ajantha Mendis.
It also appointed former captain and batting great Sanath Jayasuriya as 'cricket consultant' on a year-long deal.
