© 2019, Springer Science+Business Media, LLC, part of Springer Nature. The purpose of the study was to identify bidirectional and longitudinal links between attributions, coping, and health functioning among adolescents with chronic illness and their parents. Religious/spiritual coping, attributional styles, and health functioning were assessed among adolescents with chronic illness at two time points approximately 21 months apart. Parental coping and attributions at both time points were also measured. Longitudinal links between variables were tested using an autoregressive cross-lagged path model; adolescent age and disease differences were evaluated via multigroup modeling. Poorer adolescent health functioning at baseline predicted higher use of parent optimistic attributional style at follow-up. Adolescent optimistic attributional style at baseline predicted more positive and less negative religious/spiritual coping at follow-up; adolescent negative religious/spiritual coping at baseline predicted more positive religious/spiritual coping at follow-up. Parent optimistic attributional style and positive religious/spiritual coping at baseline predicted the same constructs among adolescents at follow-up. With respect to age differences, parental negative religious/spiritual coping at baseline was associated with poorer health functioning among younger, but not older, adolescents at follow-up. There were no disease differences in the model. Important links were identified in this family-based model of coping, attributions, and health functioning. The results highlight specific targets for interventions to improve health functioning and coping among adolescents with chronic illness, including parental religious/spiritual coping and adolescent attributional style.