The 36-year-old veteran, who has the support of Sri Lanka's sports minister, was added almost two weeks after the initial 16-man squad was announced.
"Marvan has been included as the 17th player in the squad," Sri Lanka Cricket media manager Samantha Algama told AFP.
Atapattu was not named in the original line-up despite chief selector Asantha de Mel saying the batsman's experience would be useful on the two-Test Australian tour.
The opener last played a Test in 2005 and did not feature during this year's World Cup. He has scored 5,330 runs in 88 Tests and 8,529 runs in 268 one-day internationals.
Atapattu had earlier lashed out at the selectors, saying he had no faith in them although he planned to play for at least two more years.
But Sports Minister Gamini Lokuge voiced support for his inclusion for Australia. Sri Lanka leave on Tuesday for two Tests in Brisbane and Hobart.
Atapattu, who is overseas, was not immediately available for comment.