While completing his family medicine residency in Thunder Bay, Ontario, he met his wife, Margaret Kruk, who is currently a professor at the Harvard T.H.

Galea worked as a medical epidemiologist at the New York Academy of Medicine's Center for Urban Epidemiologic Studies from 2000 to 2005 and was promoted to associate director in 2002.

From 2008 to 2009, he directed the Center for Global Health at the University of Michigan in Ann Arbor, and served as a board member and vice president of the International Society for Traumatic Stress Studies.

[3] Galea's research has highlighted the link between specific social environment factors and the incidence, comorbidity, and progression of anxiety, mood, and substance use disorders.

By applying novel analytic methods, he advanced classic psychiatric epidemiology, emphasizing the impact of social and economic forces on these disorders.

His work also focused into the causes and effects of accidental drug overdose, leading to public health interventions aimed at reducing overdose-related morbidity and mortality in urban areas.

[20][21][22] Galea's work also documented the mental health sequelae of many of the largest human-made and natural disasters worldwide.

Additionally, he also conducted inquiry into the consequences of trauma and conflict on military service members and reservists worldwide.