The objective of this study was to examine whether cognitive change and age predicted work outcome in the context of supported employment (SE) and compensatory cognitive training (CCT) in severe mental illness. Forty unemployed outpatients receiving SE (7 young [20–35 years], 15 middle-aged [36–50 years], and 18 older [51–66 years] patients) completed cognitive assessments at baseline and after 12 weeks of CCT. Logistic regression analyses showed that improvement in attention/vigilance significantly predicted work attainment (B = 2.35, SE = 1.16, p = 0.043). Young and older participants were more likely to obtain work than middle-aged participants (B = 4.03, SE = 1.43, p = 0.005; B = 2.16, SE = 0.93, p = 0.021, respectively). Improved attention and age group (young and old) were associated with better work outcomes after SE + CCT. Improving attention may be an important target for improving work outcome in severe mental illness. Middle-aged individuals may need additional support to return to work.