OBJECTIVE The effectiveness of postoperative medication for the prevention of late graft failure is controversial. We conducted the present study to investigate whether cilostazol improved the mid-term outcomes after infrainguinal autologous vein bypass for chronic limb-threatening ischemia (CLTI). METHODS From April 1994 to March 2022, we performed 590 de novo infrainguinal bypass procedures using autologous vein grafts (AVGs) in three hospitals. The bypass grafts were classified according to the postoperative prescription of cilostazol. The loss of graft patency and major adverse limb events (MALEs) were set as endpoints. Patients who died within 30 days and grafts that lost primary patency within 30 days after surgery were excluded. Data up to 3 years were analyzed. The cumulative primary patency (PP), assisted primary patency (AP), secondary patency (SP), and freedom from MALE (ffMALE) rates were calculated by the Kaplan-Meier method and compared between the cilostazol group and the non-cilostazol group. After a propensity score matching, same statistical analyses were performed. In addition, a Cox proportional hazards regression analysis that included preoperative factors, intraoperative factors, and postoperative medications was performed to identify whether cilostazol is an independent predictor for the outcomes. RESULTS A total of 523 AVGs met inclusion criteria. Kaplan-Meier curves showed that the cilostazol group was superior to the non-cilostazol group in all outcomes, while the cilostazol group was superior to the non-cilostazol group in AP and SP after a propensity score matching. A multivariable analysis showed that non-use of cilostazol was identified as an independent predictor for loss of AP, SP, and ffMALE. CONCLUSIONS Cilostazol improved the mid-term outcomes after infrainguinal autologous vein bypass.