Self-rated health (SRH) is an important predictor of objective health-related outcomes that, according to the Cognitive Process Model of SRH, is influenced by contextual factors (symptoms and personality). Although research indicates that personality contours SRH, less attention has been given to understanding the contributions of personality to future self-rated health (FSRH) or the contextual factors that play a role in shaping these effects.The aim of the present study was to extend the theory and research on FSRH by exploring the contributions of personality, current SRH, and fatigue to FSRH in the context of chronic illness, and to test the potential mediating role of optimism for explaining these effects.Two chronic illness samples (arthritis, N = 365, and inflammatory bowel disease, IBD; N = 290) completed identical surveys. A hierarchical regression model with age, education, and current health, and fatigue entered in the first two steps and traits entered in the last step, tested the effects of personality on FSRH. Mediation analyses controlling for contextual variables tested the explanatory role of optimism.Fatigue was a significant contributor to FSRH accounting for 11 % of the variance in the arthritis sample and 17 % in the IBD sample over the demographic variables. Both Agreeableness and Neuroticism accounted for additional significant but modest variance in FSRH (4 %); Agreeableness was associated with higher FSRH, whereas Neuroticism was associated with lower FSRH. For both traits, optimism fully explained the associations with FSRH.After accounting for the influence of fatigue and other variables, the contributions of high Agreeableness and low Neuroticism to FSRH are modest in the context of chronic illness, and these associations may be explained by optimism.