This is the first Canadian longitudinal study to use province-wide clinical administrative data to explore when family reunification is most likely to occur and for whom. Clinical administrative child protection data were merged with the 2006 Canadian Census data for the province of Québec; the final dataset included 24,196 children admitted to out-of-home care for the first time between April 1, 2002 and March 31, 2011, of which 80.2% (N = 19,412) return to live in their natural family milieu. The overall cohort was divided into two groups: children 0 to 9 years old (N = 8369) at initial placement of which 68.9% return to live in their natural family milieu; and children 10 to 17 years old (N = 15,827) at initial placement of which 86.3% return to live in their natural family milieu. Cox proportional hazard results indicate that younger children, specifically those aged 2 to 5 years old at initial placement, have the lowest likelihood of returning to live with their natural families over time. Irrespective of age at initial placement, the decreased likelihood of family reunification was statistically explained by a combination of psychological abuse, physical and health neglect, parents' high risk lifestyle, sexual abuse, school neglect, hospital referrals, placement instability, number of investigations, and neighborhood area socioeconomic disadvantages.