Rheumatoid arthritis (RA) is associated with an increased risk of cardiovascular disease (CVD). Advanced measures of cardiorespiratory fitness (CRF) are associated with CVD risk factors. The present study aimed to examine whether CVD risk factors can predict clinic-based measures of CRF, using the Siconolfi step test and to determine if exercise can improve RA patients’ cardiovascular health. Sixty-five RA patients (46 females, age 58 ± 11 years) completed assessments of CRF, CVD risk factors, body composition and RA characteristics. Ten patients participated in a follow-up 8-week exercise intervention. CRF was low (22 ml kg−1 min−1) and associated with higher diastolic blood pressure (r = − 0.37, p = 0.002), higher global CVD risk (r = − 0.267,  p = 0.031) and worse body composition profile (body fat, r = − 0.48, p < 0.001; waist, r = − 0.65, p < 0.001; hip, r = − 0.58, p < 0.001). Regular exercise significantly improved CRF (p = 0.021), lower body strength (p < 0.001), agility (p < 0.001), systolic blood pressure (p = 0.021), body fat (p = 0.018), waist circumference (p = 0.035), hip circumference (p = 0.016), disease activity (p = 0.002), disability (p = 0.007) and QoL (p = 0.004). Elevated diastolic blood pressure and worse body composition profile are strong predictors of clinic-based measures of CRF. CRF is an important determinant of CVD risk and warrants inclusion in the routine assessment of RA patients. Regular exercise can improve CRF and CVD risk factors without any exacerbation of disease activity and should be offered as part of routine care.