Background: Exercise is one of the optimal and alternative treatments for type 2 diabetes (T2DM). Although the effect of a single bout of exercise on insulin sensitivity is reported to persist only for 2–3 days, effects remain unclear of a 12‑week aerobic exercise training on insulin sensitivity, quality of life (QOL), and depression status over time as exercise training duration increases in patients with T2DM. Objectives: To investigate the effects over time in patients with T2DM of a 12‑week aerobic exercise training on insulin sensitivity, QOL, and depression status. Materials and Methods: Purposive sampling was used to recruit 17 T2DM patients. Participants underwent a 12‑week, supervised, moderate‑intensity aerobic exercise training three times per week, 30 min per session. Outcome indicators including insulin sensitivity (measured by a 2‑h oral glucose tolerance test [OGTT] and homeostatic model assessment‑insulin resistance [HOMA‑IR]), QOL (Medical Outcomes Study Short Form 36), and depression status (beck depression inventory scale) were evaluated at baseline and at 4‑week intervals. Results: A final 13 eligible participants completed the study. For every 4‑week increase in duration of exercise training, there was an increase over time in insulin sensitivity, including a decrease over time in OGTT glucose area under the curve of 66.92 min/mmol/L. Glucose concentrations decreased over time at 60, 90, and 120 min after an oral glucose challenge. Further, the HOMA‑IR decreased over time as the duration of exercise training increased. QOL and depression status improved significantly during the training. Conclusions: Moderate‑intensity exercise training improves insulin sensitivity, QOL, and depression status in T2DM patients, particularly over time within a 12‑week exercise training course.