Background: Various types of flaps are considered as reconstructive options for patients with diabetic foot ulcer (DFU). However, flap reconstruction for DFU treatment is particularly challenging because of the relatively limited collateral perfusion in the distal lower extremity. This study evaluated the efficacy and safety of a novel postoperative monitoring procedure implemented in conjunction with NPWT immediately after flap operations for treating diabetic foot. Methods: A retrospective analysis was performed on DFU patients who underwent free flaps and perforator flaps from March 2019 through August 2021. The surgical outcomes of interest were the rates of survival and complications. On the third postoperative day, patients underwent computed tomography (CT) angiography to check for pedicle compression or fluid collection in the sub-flap plane. Monitoring time, as well as comparisons between NPWT and conventional methods, were analyzed. Statistical analysis was performed between the two groups. Results: This study included 26 patients. Among DFU patients, the NPWT group included 14 flaps and the conventional monitoring group included 12 flaps. There was no significant intergroup difference in flap survival rate (p = 0.83). In addition, there was no significant intergroup difference in the diameters of perforators or anastomosed vessels before and after NPWT (p = 0.97). Compared with conventional monitoring, the novel NPWT monitoring system was associated with a significantly lower mean monitoring time per flap up to postoperative day 5. Conclusion: Although conventional monitoring is widely recommended, especially for DFU management, the novel NPWT monitoring system investigated in this study enabled effortless serial flap monitoring and was associated with reduced infection risk compared with conventional monitoring. The novel flap monitoring technique was safe for DFU patients and is a promising candidate for future recognition as the gold standard for flap monitoring.