Kawshalya Madushani gained her first international experience in 2014 at the Junior Asian Championships in Taipei , where she won the silver medal in the hurdles in 1: 02.31 min and with the Sri Lankan 4 x 400 meter relay in 3: 47.86 min came in fifth place. In 2016 she took part in the South Asian Games in Guwahati for the first time and won the bronze medal there in 59.87 seconds behind the two Indian women Jauna Murmu and Ashwini Chidananda Akkunji . Three years later she won the silver medal in the hurdles at the South Asian Games in Kathmandu in 1: 00.40 min behind Najma Parveen from Pakistan and finished fifth in the 400-meter run in 55.63 s. In addition, she won the Sri Lankan season in 3: 41.10 min.
In 2016, 2017 and 2019, Madushani became Sri Lankan champion in the 400-meter hurdles.