Background: The defect size of an osteochondral lesion of the talus is one of the most important prognostic factors for deciding clinical outcomes. However, the prognostic factors for small osteochondral lesions of the talus are unknown. Purpose: To investigate the significant prognostic factors for small osteochondral lesions of the talus using arthroscopic bone marrow stimulation techniques. Study Design: Case series; Level of evidence, 4. Methods: Fifty ankles in 50 patients treated with arthroscopic bone marrow stimulation techniques for an osteochondral lesion of the talus (<150 mm2) were evaluated for prognostic factors. The patients were 22 men and 28 women (mean age, 35.0 years). Outcomes were measured using the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale, Berndt and Harty scale, and Saxena criteria. Results: The mean lesion size was 62 mm2 (range, 7-119 mm2). The mean AOFAS score improved from 74 (range, 18-90) preoperatively to 90 (range, 67-100) postoperatively. The Saxena criteria results were excellent, good, fair, and poor in 36 (72%), 8 (16%), 5 (10%), and 1 (2%) patients, respectively. The Berndt and Harty scale results were good in 34 (68%), fair in 6 (12%), and poor in 10 (20%) patients. Linear regression analyses showed prognostic significance for lesion depth and outcome. Medial lesions had a significantly higher incidence of poor outcomes than lateral lesions (P < .05). Among the medial lesions, lesions uncovered with the medial malleolus had inferior outcomes compared with covered lesions (P < .0001). There was no association between clinical outcome and lesion size or body mass index. In older patients (≥40 years), there was a significant trend toward inferior clinical outcomes (P < .05). Conclusion: Arthroscopic bone marrow stimulation techniques provided satisfactory clinical outcomes. However, older patients, deep lesions, and medial lesions uncovered with the medial malleolus were associated with inferior clinical outcomes.