Background/Objectives: As a representative anatomic ankle ligament repair technique, the Broström procedure continues to be modified to reach better clinical outcomes, superior mechanical stability, early rehabilitation, and minimal risk of recurrent instability. This study aimed to evaluate the intermediate-term clinical outcomes after the modified Broström procedure (MBP) with suture-tape augmentation for chronic lateral ankle instability. Methods: Ninety-four patients with chronic lateral ankle instability were followed for ≥3 years after MBP augmented with suture tape. The patient-reported clinical outcomes were evaluated with the Foot and Ankle Outcome Score (FAOS) and the Foot and Ankle Ability Measure (FAAM). The changes in mechanical ankle stability were evaluated with physical examination and periodic stress radiography. The changes in static and dynamic postural control ability were assessed with the single-leg stance test and Biodex posturography. Results: FAOS and FAAM scores significantly improved from preoperative means of 52.6 and 54.2 points to 91.8 and 90.5 points at final follow-up, respectively (p < 0.001). Talar tilt angle and anterior talar translation significantly improved from preoperative means of 15.4° and 14.3 mm to 2.7° and 4.5 mm at final follow-up, respectively (p < 0.001). Two patients (2.1%) complained of a recurrence of mechanical and functional instability. One patient (1.1%) showed non-specific inflammation related to a suture tape. Balance retention time significantly improved from a preoperative mean of 3.7 to 6.4 s at final follow-up (p < 0.001), with a non-significant side-to-side difference. The overall stability index significantly improved from a preoperative mean of 3.7 to 1.9 at final follow-up (p < 0.001), with a significant side-to-side difference. Conclusions: The MBP augmented with suture tape appears to be an effective surgical technique for chronic lateral ankle instability. Through anatomic repair of attenuated ankle ligaments and suture-tape augmentation, this modified procedure can provide reliable stability and minimal risk of recurrent instability. In addition, static and dynamic postural control ability may be improved through continuous proprioceptive-oriented rehabilitation following surgery.