Dennis joined the API in 1983 and is a current Fellow member. He is a Past President of the Australian Property Institute (WA Division) having served as the President over the period 2011 to 2013. Dennis was also was chairman of the Marketing and Communication and Regional State Conference Committees of the API, serving on the Divisional Council for 9 years.

He was reappointed to the Western Australian Committee in October 2017.

Dennis was also the Australian Property Institute (WA Division) appointed National Council Representative for the 12 month period ending May 2015, overseeing a period of significant structural change for the API, at both a National and State level.