This study examined factors associated with mental health services (MHS) use by individuals with mental disorders within a developmental perspective of adulthood. Bivariate and multivariate analyses were conducted separately for each developmental stage on independent variables using the Andersen's behavioral health service model. For 18-29-year-old emerging adults (n = 141), autonomy, daily life/relations, Internet searching, alcohol dependence, cognitive impulsiveness, number of stressful events, and self-harm were associated with MHS use. For 30-49-year olds (n = 292), being female, country of origin, being on welfare, social integration, Internet searching, and number of stressful events were associated with MHS use. For 50-64-year-old middle-aged adults (n = 126), current occupation was associated with MHS use. Developing online resources for emerging adults may increase MHS use. For 30-49-year olds, outreach should target male, immigrants, and individuals less socially integrated and on welfare. For middle-aged adults, workplace programs that reduce stigma and offer psychological help could increase MHS use.