Idiopathic inflammatory myopathies (IIM) are a group of rare and complex autoimmune diseases, characterised by inflammatory involvement of skeletal muscles and often involving skin and other organs. Vasculopathy is key to the pathogenesis of these conditions and is an important factor influencing morbidity and mortality. Nailfold capillaroscopy, allowing visualisation of the end row loop of capillaries at the fingernail, can provide a window into the circulation that reflects capillary drop out seen in tissues such as muscle and skin. Nailfold capillaroscopy is increasingly recognised as a valuable tool aiding diagnosis of IIM, in particular juvenile dermatomyositis (JDM), dermatomyositis (DM), anti-synthetase syndrome and overlap conditions where nailfold abnormalities are frequent. These abnormalities, particularly decreased nailfold capillary density or a ‘scleroderma pattern,’ can associate with disease activity and organ involvement, making nailfold capillaroscopy a helpful tool for disease monitoring. In this chapter, we aim to show how nailfold capillaroscopy is useful to clinicians in diagnosis and disease monitoring. We describe nailfold capillary findings in IIM and similarities/differences compared to other diseases such as systemic sclerosis. The chapter includes a summary of the evidence supporting the use of NFC in juvenile DM and DM as well as possible future research directions.