As a researcher, Jacques Tremblay has contributed to the field of clinical epidemiology, with the introduction of Drug Use Review, a quality assurance approach to medical prescribing, and assessment of the quality of medical care with explicit criteria in Canada. He has conducted effectiveness studies in the treatment of substance abusers and persons presenting with chronic post-traumatic stress disorder. He has been a Carnegie Commonwealth Fund Research Fellow, a Robert Wood Johnson Foundation Clinical Scholar, and a Health & Welfare Canada Research Fellow and National Health Scholar.

His current research contributes to three main domains: a)epidemiological catchment area studies in mental health in the South-West of Montreal; b) community mental health research in low and middle income countries; and c) the clinical assessment of: i)substance use (i.e. alcohol abuse) disorder treatment effectiveness; ii) persons driving under the influence of alcohol; iii) PTSD and trauma-related disorders; iv) planning and delivery of integrated mental health services in Québec; and v) effectiveness of treatment in chronic post-traumatic stress disorder related to invasive memories.