Asalanka will be the vice-captain for the five-match Twenty20 series in Australia next February.
The 24-year-old all-rounder who also captained the Sri Lanka Under-19 team, has so far scored 295 runs in nine Twenty20 Internationals.
However, Bhanuka Rajapaksa has not been named in the squad and Wanindu Hasaranga and Avishka Fernando have been named in the squad again.
Newcomers Janith Liyanage and Kamil Mishara have also been included in the squad.
Sri Lanka T20 squad to tour Australia:
Dasun Shanaka (Leader), Charith Asalanka (Deputy Leader), Avishka Fernando, Pathum Nissanka, Danushka Goonetileke, Kusal Mendis, Dinesh Chandimal, Chamika Karunaratne, Janith Liyanage, Kamil Mishara, Ramesh Mendis, Wanindu Hasaranga, Lahiru Kumara, Nuwan Thushara, Dushmantha Chameera, Binura Fernando, Mahesh Theekshana, Jeffrey Vandersay, Praveen Jayawickrama and Shiran Fernando.