The glenohumeral ligaments are important structures for the stability of the shoulder. They are integrated parts of the capsule and are at risk to be injured in a traumatic shoulder dislocation. The aim was to examine the prevalence of capsular ligament lesions in the acute phase and at minimum 3 weeks' follow-up after first-time traumatic shoulder dislocation. Forty-two patients aged 16–40 years were included. All patients underwent computed tomography and magnetic resonance imaging (MRI) scans shortly after the injury and MR-arthrography (MRA) at follow-up. The median time from dislocation to MRI was 7 (range 2–14) days and to MRA 30 (range 21–54) days. We found capsular ligament lesions in 22 patients (52.4%) in the acute stage and in five patients (11.9%) at follow up. Nine patients (21.4%) had a humeral avulsion of the anterior glenohumeral ligament (HAGL lesion) on MRI. Three patients (7.1%) had this lesion at follow-up. The rate of HAGL lesions in the acute stage was higher than reported previously, but the prevalence at follow-up was in keeping with earlier published studies.