120 patients with chronic lateral epicondylitis were randomized to receive injections of either autologous conditioned plasma (ACP) or betamethasone. The purpose of this trial was to compare scores of the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire and pain levels post injection to determine if ACP provided clinical benefits in comparison to steroid injections. The results of this trial indicated that betamethasone provided better DASH scores at 6 weeks and 6 months, but by 1 year, the ACP group demonstrated significantly better DASH results. Additionally, the betamethasone group consistently reported greater rates of full recovery throughout 1 year of follow-up, but ACP had more patients report very good or good DASH scores when assessed at 1 year. ACP treatment of the lateral epicondylitis may provide a longer-term therapeutic effect, whereas betamethasone yields rapid improvement.