Symptomatic ulnar nerve (UN) dislocation is an under-recognized cause of medial elbow pain in overhead athletes. Traditionally, surgery has been considered when symptoms persist; however, advances in dynamic ultrasound (US) and US-guided targeted interventions may enable conservative treatment. Reports on long-term return to play (RTP) after US-guided physiotherapy remain scarce. A 20-year-old right-handed collegiate sidearm pitcher developed progressive medial elbow pain for one year, with acute worsening two weeks before presentation. Clinical examination suggested ulnar collateral ligament (UCL) strain and concomitant neurogenic thoracic outlet syndrome (N-TOS). Dynamic US revealed an anterior UN dislocation over the medial epicondyle during elbow flexion, which reproduced the patient's pain. Management was performed using a stepwise strategy. Phase 1 targeted the proximal contributors (N-TOS) using scapular and chin retraction exercises combined with neural mobilization. Phase 2 addressed the primary distal pathology with US-guided perineural soft tissue mobilization, and skin-pinch traction was applied until movement of the myofascial trilaminar retinaculum (MTR) was confirmed under US, thereby improving the perineural tissue. This was followed by pain-free UN-sliding exercises. After 12 weeks, neural tension signs subsided, and pain during dynamic UN displacement diminished. A graded throwing program was completed, enabling RTP at five months. At the two-year follow-up, the athlete remained asymptomatic without recurrence, despite persistent painless dynamic subluxation on US. In this single-case report of an athlete with UN dislocation complicated by N-TOS, a stepwise, ultrasound-guided, target-specific physiotherapy approach is presented as a hypothesis-generating example of conservative management. The intervention, which included direct mobilization of the myofascial trilaminar retinaculum, facilitated a safe return to play, and no surgical intervention was required during the treatment course. In this case, ultrasound was used provisionally to monitor clinically relevant changes, such as visible improvement in neural gliding and reduction of perineural soft tissue irritation. Rather than serving as a generalized recommendation, these observations suggest a potential rationale for incorporating ultrasound into conservative management pathways.