The South Asian Football Federation (SAFF) women’s cup, which runs until November 20, features eight teams including Pakistan’s arch-rivals India and neighbour Afghanistan.
The tournament is the first high-profile regional women’s sports event in Pakistan.
A young home-side were contained in their own half for most of the match by a composed Sri Lanka team, going one down before half time to a goal from midfielder Ishara Madushani.
After the break Pakistan had several chances to equalise, but Sri Lankan forward I.L.E. Kumudumala added a second goal in the 86th minute.
On the stroke of full-time, Pakistan captain Hajra Khan scored a face saving goal in the 89th minute.
Pakistan skipper Khan said the tournament would give her youthful side good experience of international competition.
“We lack exposure, I am pretty sure if we get more international exposure, we can perform well,” she told AFP.
“We are a very young team and I think we gave them a good fight specially in the second half.”
The Pakistan Football Federation (PFF) promised tight security for the teams, after a suicide attack at a border post with India last week killed nearly 60 people. Doubts had been raised over whether the tournament would go ahead following the incident.
Monika Staab, a FIFA consultant for women football, told AFP she had no security worries and said the tournament would send a good signal to budding young female players.
“I hope all parents watching this and give the girls permission to play,” she said.
“It’s a beautiful game and it’s not only for the boys, it’s also for girls.”
India will play their opening game against Maldives in a group A match on Thursday while Afghanistan will face Bangladesh on the same day. Nepal take on Bhutan in the second match of the group B Wednesday.