Background: Limited ankle dorsiflexion (DF) range of motion (ROM) is associated with mechanical dysfunctions and chronic ankle instability. Uphill treadmill walking exercise (UTWE) has the potential to improve ankle mobility and function. Objects: This study aimed to examine the immediate effects of a 15° UTWE on DF ROM and torque generation in patients with limited DF. Methods: The study included 20 adults, comprising 10 males and 10 females, with a mean age 28 years and a passive DF range of 5°–12°. After baseline assessments, participants completed 30 minutes of UTWE on a 15° incline treadmill, followed by post-assessments. DF ROM was evaluated during the stance phase of gait, and in both open-kinematic-chain (OKC) and closed-kinematic-chain (CKC) conditions using a goniometer and Image J software. DF and plantar flexion (PF) peak torque were measured with a Biodex Dynamometer. Results: Post intervention, maximum DF ROM during the stance phase of gait increased significantly from a mean of 8.54° ± 3.97° to 11.03° ± 4.41°. The DF ROM in the OKC and CKC conditions increased significantly from a mean of 8.90° ± 0.62° and 21.55° ± 0.72° to 18.00° ± 1.13° and 28.20° ± 1.00°, respectively (p < 0.0001). DF peak torque increased from 16.20 ± 1.28 N/m to 21.52 ± 1.39 N/m, and PF peak torque increased from 25.26 ± 2.51 N/m to 44.22 ± 4.20 N/m (p < 0.0002). Conclusion: UTWE significantly enhanced DF ROM and ankle torque, indicating that it may be an effective intervention for improving ankle function and preventing injury in clinical and rehabilitation settings.