Multiple treatment options have been shown to improve dorsiflexion range of motion (DFROM) group means in patients with chronic ankle instability (CAI). However, not all patients with CAI respond equally to these treatments. The aim of this study was to identify predictors of successfully improving dorsiflexion range of motion (DFROM) in patients with CAI. Patients with <11.41 cm of DFROM had a 98% probability of a meaningful DFROM improvement following ankle joint mobilizations. Individual predictors of success for plantar massage and calf stretching were also identified and resulted in >92% posttest probabilities. Simple pretreatment assessments can dramatically improve treatment success probability following STARS in patients with CAI.