After his graduation from University of Colombo with a degree in physical sciences he joined the Sri Lanka Police service on 16 June 1986, beginning his career as an Intelligence Officer with the rank of ASP.
On the 26 April 2019, President Maithripala Sirisena ordered the then Inspector General of Police, Pujith Jayasundara, to resign over intelligence failures that led to the fatal Easter bomb attacks.
[2][3] The temporary appointment became a controversy as Jayasundara denied the allegations levelled against him by the President filed a court case against the government regarding the intelligence lapse.
Wickramaratne was a Senior Deputy Inspector General, when he was appointed to the role of acting Inspector-General of Police, when the incumbent, Jayasundara, was suspended following the 2019 Easter bombings.
[7] He also ordered a special investigation to probe statements made by former LTTE cadre Karuna Amman, who claimed to have killed more than 3000 army soldiers at the Elephant Pass during the civil war.