Withana has held management positions in the corporate sector for over 25 years, during which he had held senior management positions in Banking, Manufacturing and Trading for more than 25 years. He has worked with many organizations such as Brandix Group, Ernst and Young, Amsterdam Rotterdam (Amro) Bank, IBM World Trade, Corporation and Carson Cumberbatch, Ceylon Tea Services Limited and Yamaha Corporation in (USA).
Withana served as the Group Chief Finance and Administrative Officer for SriLankan Airline and later as the Chief Executive Officer in its subsidiary SriLankan Catering till very recently.
He is currently serving as the Founder and Managing Director of Agility Consulting Services (Pvt.) Ltd and as a Board Director of Laugfs Gas PLC, Laugfs Maritime Services (Pvt.) Ltd and Softlogic Life Insurance PLC.
He is also currently serving on the Board of Acuity Partners (Pvt.) Ltd, and as Vice President of the Project Management Institute, Colombo Chapter, and is also serving on the executive committee of the Sri Lanka National Olympic Committee.
He had previously served as an Independent Director on the Boards of Bank of Ceylon, Dankotuwa Porcelain PLC, Merchant Bank of Sri Lanka PLC, Ceylease Limited and Seylan Bank.
Withana had also been a Commissioner of the Telecommunication Regulatory Commission of Sri Lanka (TRCSL). He is a fellow member of the both Chartered Institute of Management Accountants (FCMA), UK, and the Institute of Chartered Accountants of Sri Lanka (FCA). He is also a Project Management Professional at the Project Management Institute (PMI), USA.