Anterior cruciate ligament reconstruction (ACLR) leads to quadriceps neuromuscular dysfunction, including impaired force control and muscle degradation. Neuromuscular electrical stimulation (NMES) is widely used in rehabilitation to improve muscle mass and strength; however, its effects on neuromuscular functions and muscle quality, such as motor unit (MU) behavior and force steadiness (FS), remain unclear. This study investigated the effects of NMES on neuromuscular function and muscle quality in individuals with ACLR who could walk normally. Ten male ACLR patients underwent NMES 3 times weekly for 6 weeks, with 30 contractions per session. Neuromuscular function was assessed via FS, maximum voluntary isometric contraction (MVIC), and MU behavior in the rectus femoris and vastus lateralis. Muscle quality was evaluated using muscle thickness (MT), echo intensity (EI), and ultrasound texture features. Measurements were taken at baseline and weeks 3 and 6. NMES significantly improved MVIC, FS, MU behavior, and muscle quality (MT, EI, and homogeneity) on the ACLR side, with significant interaction effects observed. At week 3, MVIC and FS showed no significant improvement; however, structural and qualitative muscle changes were evident. NMES effectively enhanced neuromuscular function, MU behavior, and muscle quality impaired by ACLR. However, a 3-week intervention may not be sufficient for optimal neuromuscular recovery, highlighting the need for extended NMES protocols.