Merrick Zwarenstein has an MD, Masters Degrees in Microbiology and in Community Health, and a PhD degree in Epidemiology. He trained as a family doctor in South Africa and worked briefly in this field before moving full time into health services research and development. He worked at the South African Medical Research Council for 18 years, where he founded the still functioning Health Systems Research Unit, before moving to the University of Toronto in 2002. He joined the Department of Family Medicine at Western University, as Director of the Centre for Studies in Family Medicine in 2013. He has around 250 peer reviewed publications including several books and book chapters.

His research work has concentrated on primary care. He has done extensive work on training for nurse led teams to substitute for physicians, which is now the national primary care policy in South Africa and spreading internationally. This work led to an interest in knowledge translation, where he researches educational and organizational approaches to closing the gap between research and clinical practice. He has also researched research methods, especially randomized trials of complex service delivery interventions, which contributed to the recent global increase in pragmatic randomized trials.