Introduction <p>The clinical benefits of high tibial osteotomy (HTO) in patients with mild varus deformity with degenerative medial meniscal tear (DMMT) remain unclear. This study aimed to compare clinical outcomes among middle-aged patients with mild varus deformity who underwent arthroscopic meniscal repair and HTO for DMMT.</p> Materials and methods <p>In this retrospective study, patients who underwent isolated arthroscopic meniscal repair via the inside-out technique and those who underwent medial opening-wedge HTO were assigned to group M and H, respectively. The inclusion criteria were: an age of 40–65 years; percentage of mechanical axis of 30–50% measured using full-length weight-bearing anteroposterior radiographs; Kellgren–Lawrence grade ≤ 2; minimum postoperative two-year follow-up; and HTO correction angle &lt; 10°. Clinical outcomes were assessed using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and minimal clinically important difference achievement rate for the KOOS subscales preoperatively and at the final follow-up.</p> Results <p>Group M and H included 21 and 41 patients, respectively. The median ages were 53 and 58 years in groups M and H, respectively. In group H, 24 cases underwent meniscal repair. No significant differences in all KOOS subscales were found preoperatively. However, the median KOOS symptoms subscale in group H (89.3) was significantly better than that in group M (80.4) at the final follow-up (<i>p</i> = 0.04).</p> Conclusion <p>The main finding of the study indicated that KOOS symptoms after HTO were superior to those after isolated arthroscopic meniscal repair for DMMT. HTO might be a potentially useful treatment for DMMT in middle-aged patients with mild varus deformity, even with a small correction angle.</p> Level of evidence <p>Retrospective comparative study, Level III.</p>