Muscle weakness is one of the main consequences following a stroke, leading to significant alterations in gait and other daily activities. Isokinetic muscle strengthening of the lower limb is considered to be an effective complement to conventional treatment to improve these functional limitations. The objective of this systematic review was to analyze isokinetic lower limb strengthening protocols and their effects on muscle strength, gait, and mobility in post-stroke patients compared to conventional physiotherapy or other strengthening methods. A systematic review of randomized controlled trials (RCTs) from the last 10 years was conducted. Studies analyzing the effects of isokinetic lower limb muscle strengthening compared to conventional physiotherapy or other strengthening methods on muscle strength, gait parameters, and mobility in post-stroke adults were selected. The quality and risk of bias of the studies were evaluated using the PEDro scale, the Oxford Level of Evidence scale, and the Cochrane Review Manager tool. Six studies met the eligibility criteria. For knee-ankle strength, gait speed, and mobility, isokinetic strengthening demonstrated significant improvements compared to conventional physical therapy. When compared to other strengthening methods, isokinetic training was more effective for hip-knee strength and mobility, while closed kinetic chain isokinetic strengthening showed greater benefits for gait speed. Additionally, in the early post-stroke phase, isokinetic training showed greater improvements, while the chronic phase demonstrated more variable results. The methodological quality of the studies was acceptable-good. Isokinetic muscle strengthening significantly improves muscle strength, gait speed, and mobility in post-stroke adults compared to conventional physical therapy, offering additional benefits over other strengthening methods. Further research is needed to evaluate its long-term effectiveness, optimize protocols, and explore the impact of treatment timing.