Mahanama joined the elite panel in 2004 and has refereed in 58 Tests, 222 ODIs and 35 T20Is to date, including refereeing in three ICC Cricket World Cups and the ICC Champions Trophy 2009.
He has made the decision to step down six months ahead of the expiry of his contract so that he can spend more time with his family and also focus on the development of his business activities in Sri Lanka.
He continued:"However, in life a time comes when one has to keep moving forward based on obligations and priorities. My time has come to devote an uninterrupted focus and attention to my family, who made massive sacrifices over the years to enable me to pursue my career for over three decades.
"The journey for almost 12 years as an ICC match referee has been amazing and something for me to reflect upon with pride and satisfaction. I have had the pleasure of meeting and working with some outstanding professionals, refereed at some great matches and visited some incredible places along the way," Mahanama was quoted as saying in an ICC media release.
"A big bouquet to all the ICC staff and Members for the kind courtesies extended. It has been nothing less than a privilege and a pleasure to work with such a wonderful group of human beings over the years.