Diabetes is a severe chronic condition that is related to decreased physical functioning. Recently, there has been growing interest in understanding how a brief report on health such as self-rated health (SRH) could be used to track changes in health status and service needs in people with diabetes. The current research aims to investigate how SRH is affected by diabetes and how diabetes could moderate the association between age and SRH. By analyzing data from 47,507 participants, with 2869 of them clinically diagnosed with diabetes, the current study found that people with diabetes had significantly poorer SRH than people without diabetes after controlling for demographic covariates (t(2868) = −45.73,p< 0.001, 95% C.I. (−0.92, −0.85), Cohen’s d = −0.85). In addition, diabetes was a significant moderator of the relationship between age and SRH (b= 0.01,p< 0.001, 95% C.I. (0.01, 0.01)). Specifically, age was more strongly related to SRH in people without diabetes (b= −0.015,p< 0.001, 95% C.I. (−0.016, −0.015)) than in people with diabetes (b= −0.007,p< 0.001, 95% C.I. (−0.010, −0.004)). Health professionals should aim to improve SRH in people with diabetes given that SRH is related to various outcomes.