Background The aim of this study was twofold: (i) to examine the association of cardiorespiratory fitness with arterial stiffness in women with systemic lupus erythematosus; (ii) to assess the potential interaction of cardiorespiratory fitness with age on arterial stiffness in this population. Materials and methods A total of 49 women with systemic lupus erythematosus (mean age 41.3 standard deviation 13.8 years) and clinical stability during the previous 6 months were included in the study. Arterial stiffness was assessed through pulse wave velocity (Mobil‐O‐Graph® 24 hours pulse wave velocity monitor). Cardiorespiratory fitness was estimated with the Siconolfi step test and the 6‐minute walk test. Results Cardiorespiratory fitness was inversely associated with pulse wave velocity in crude analyses (P < .05), although this relationship was attenuated when age and other cardiovascular risk factors were controlled. There was a cardiorespiratory fitness × age interaction effect on pulse wave velocity, regardless of the test used to estimate cardiorespiratory fitness (P < .001 for the Siconolfi step test; P = .005 for the 6‐minute walk test), indicating that higher cardiorespiratory fitness was associated with a lower increase in pulse wave velocity per each year increase in age. Conclusions The results of this study suggest that cardiorespiratory fitness might attenuate the age‐related arterial stiffening in women with systemic lupus erythematosus and might thus contribute to the primary prevention of cardiovascular disease in this population. As the cross‐sectional design precludes establishing causal relationships, future clinical trials should confirm or contrast these findings.