Although idiopathic inflammatory myopathies (IIM) are a heterogeneous group of diseases nearly all patients display muscle inflammation. Originally, muscle biopsy was considered as the gold standard for IIM diagnosis. The development of muscle imaging led to revisiting not only the IIM diagnosis strategy but also the patients’ follow‐up. Different techniques have been tested or are in development for IIM including positron emission tomography, ultrasound imaging, ultrasound shear wave elastography, though magnetic resonance imaging (MRI) remains the most widely used technique in routine. Whereas guidelines on muscle imaging in myositis are lacking here we reviewed the relevance of muscle imaging for both diagnosis and myositis patients’ follow‐up. We propose recommendations about when and how to perform MRI on myositis patients, and we describe new techniques that are under development. Muscle imaging and especially muscle MRI is a powerful technique for both IIM diagnosis and follow‐up. Muscle MRI is actually the best muscle imaging technique in routine, and it is widely used, but guidelines determining when and how to use it in myositis patients are lacking.