[10] She started playing cricket at the age of nine at her residence in Kotikawatta where she was born and her father provided enormous support and guidance to take up the sport to the highest level.

She was graduated from the President's College, Sri Jayawardenapura Kotte where she also pursued athletics as there was no women's cricket team attached with the educational institute.

[15] She also indicated that she was thoughtful about retiring from international cricket in 2013 after her marriage but her husband convinced her to continue to play for Sri Lanka.

[7] Siriwardene made her ODI debut against West Indies at Kingstown, St. Vincent in March 2003 at the age of 18 after being selected to the national pool in 2002.

She was part of the Sri Lankan side which became runners-up to India in the inaugural edition of the Women's Asia Cup in 2004.

She made her captaincy debut at the age of 20 years in a group stage match against Pakistan as part of the 2005–06 Women's Asia Cup at Karachi which Sri Lanka eventually won by 14 runs.

[23][24][25] She captained the side at the 2009 Women's Cricket World Cup where Sri Lanka failed to win a single game and was knocked out of the tournament.

[29] Under her captaincy, Sri Lanka qualified to Super Sixes stage for the first time ever in a Women's World Cup tournament whereas Sri Lanka sprung surprises with shocking upset victories over much fancied England and India sides during the group stage of the 2013 World Cup campaign.

[37] Despite her 38.29% winning percentage as captain, she is regarded as the best woman cricketer to play the game for Sri Lanka.

[42] In 2015, she was reappointed as the skipper of the Sri Lankan team and commenced her third stint as captain who resigned from the position in 2014 citing administration issues and hurdles.

[44][45] On 1 December 2016, she won the Sri Lanka Cricket awards for the Women's ODI all rounder of the Year 2016.

[47] However, she was available for team selection and captained the Sri Lankan side at the 2016 Women's T20 World Cup except for the final group stage match against South Africa after recovering from injuries.

[48] In August 2016, Siriwardane also met with an accident in Colombo after returning to cricket three and half months following the left hamstring injury which she sustained during the 2016 Women's T20 World Cup.

She underwent surgery in order to reconstruct her ACL and therefore missed out on to play against Australia and New Zealand in home bilateral international series as part of the ICC Women's Championship which began in 2017.

[51] In October 2018, she was named in Sri Lanka's squad for the 2018 ICC Women's World Twenty20 tournament in the West Indies.

[58] In January 2020, she was named in Sri Lanka's squad for the 2020 ICC Women's T20 World Cup in Australia.

[62] During the 2020 T20 World Cup, Indian women's team felicitated Shashikala with a signed jersey after the end of the group stage match between India and Sri Lanka.

[76] In March 2021, she criticised the Sri Lanka cricket selectors for being incompetent about making policies and strategies towards taking women's cricket to next stage and admitted the fact that the selectors are not convinced with her continue to play for Sri Lanka Navy club in women's inter-club limited overs competition.