90 patients with chronic ankle instability were randomized to either 3 weeks of joint mobilization treatment, 3 weeks of sham mobilization treatment, or no intervention. Patients were assessed following the completion of one session, at the completion of the 3-week treatment phases, and at 6-month follow-up after the completion of treatment for range of motion in dorsiflexion, the Cumberland Ankle Instability Tool, and the Star Excursion Balance Test in the anterior, posteromedial, and posterolateral directions. Results significantly favoured the mobilization group compared to both sham and control groups after 3 weeks and at 6-month follow-up outcome for all measures. Additional, range of motion in dorsiflexion and the SEBT-anterior test significantly favoured the mobilization group compared to both sham and control groups following one session.