Purpose: To investigate the impact of diagnosis, co-morbidity, secondary conditions (e.g. learning problems, subclinical mental and somatic complaints, addictions, and socio-emotional and behavioral problems) and problems in social context on work ability as assessed by Insurance Physicians (IPs) in young adults applying for a disability benefit. Method: IPs of the Social Security Institute assessed young adults with disabilities (aged 15-27) applying for a disability benefit (n = 1755). Data were analyzed with multilevel ordinal regression techniques. Results: Primary diagnosis, co-morbidity and subclinical mental complaints were associated with IP-assessed work ability. Persons with mental health conditions as primary diagnosis were less likely to reach a higher work ability than persons with somatic diseases. Young adults with two or more co-morbid conditions and those with psychiatric or developmental co-morbidity were less likely to reach a higher work ability level than persons without co-morbidity. Young adults with subclinical mental complaints were half as likely to reach a higher IP-assessed work ability than young adults without this condition. Conclusion: Primary diagnosis, type and number of co-morbid conditions and subclinical mental complaints are associated with IP-assessed work ability. Work-ability assessments among adolescents with disabilities applying for disability benefits still focus mainly on medical factors. © 2013 Informa UK, Ltd.