The increased migration of skilled workers globally has led to a focus in the immigration literature on the economic costs of unsuccessful labour market integration. Less attention has been given to the consequences of employment difficulties, such as those related to over-education, on aspects of immigrants' subjective well-being. Although a large proportion of immigrants experience over-education, studies examining the relationship between over-education and life satisfaction tend to concentrate on the general population. These studies find a negative relationship between over-education and life satisfaction. Since immigrant and Canadian-born (non-immigrant) workers may experience over-education differently, it is important to examine this relationship in both groups. This study examines how over-education is associated with life satisfaction among university-educated immigrant and non-immigrant workers in Canada, and accounts for differences in the degree of over-education in each group. Results indicate that overeducation was negatively associated with life satisfaction among immigrants and non-immigrants, although the effect was weaker in the immigrant population. Income was the main factor mediating the negative relationship between over-education and life satisfaction among immigrants. Furthermore, this relationship weakened with immigrants' increased residence in Canada. This may suggest that over-education is less influential in immigrants' assessment of life satisfaction over time, or the effect of over-education is weaker among earlier arrival cohorts. Results also indicated that the negative relationship between over-education and life satisfaction was weaker for immigrants from developing countries compared with those from developed countries.