Objective. The occurrence of calcinosis cutis as a clinical feature of dermatomyositis in adult patients is not well understood. Cohort studies of adult patients with calcinosis are rare. We systematically describe the clinical features, treatments and outcomes of adult patients with calcinosis. Methods. We initially enrolled 627 adult DM patients. Of those enrolled, 35 (5.6%) were found to have calcinosis. We analysed the clinical features associated with calcinosis in this subgroup. The risk factors associated with calcinosis were analysed using the Poisson regression model. Results. Multivariate analysis showed that a younger age at disease onset [odds ratio (OR) = 0.945, 95% CI 0.925, 0.966, P< 0.001], dysphagia (OR = 2.609, 95% CI 1.189, 5.728, P = 0.017), skin ulcer (OR = 5.705, 95% CI 3.041, 10.705, P< 0.001) and the presence of anti-nuclear matrix protein 2 antibody (OR = 5.917, 95% CI 2.754, 12.714, P< 0.001) were independently associated with calcinosis. In both the low- and high-dose prednisone treatment groups, no difference in treatment response was seen between the bisphosphonate treatment group and the group not receiving bisphosphonate treatment (P = 1.000 and P = 0.375, respectively). A follow-up study revealed that the mortality rate of the calcinosis group was 5.7%. Additionally, 60.6% of the cases had a chronic polycyclic disease course and 17.1% had mild complications secondary to calcinosis. Conclusion. Calcinosis is an uncommon, but significant clinical feature in adult patients with DM. Bisphosphonates were not found to effectively treat calcinosis, however, the overall health outcomes of adult DM patients with calcinosis were favourable.