Sixty patients with a diagnosis of osteoarthritis and scheduled for a unilateral total hip arthroplasty (THA) via a minimally invasive Watson-Jones approach were randomized to receive the operation in a supine position or a lateral position. The primary outcome of interest was acetabular cup position, measured radiographically as the absolute target error of acetabular cup inclination and anteversion. Additional outcomes included the Japanese Orthopaedic Association (JOA) score, operative time and intraoperative blood loss. Follow up was performed 3 months post-operation. Results revealed significantly lower absolute target error of acetabular cup inclination in the supine group compared to the lateral group. No significant difference in the absolute target error of acetabular cup anteversion was observed between the two groups. No significant differences in JOA score, operative time or intraoperative blood loss were observed between the supine and lateral groups.