Aims <p>Diabetes mellitus (DM) is one of the most common chronic diseases globally, and most patients suffer from a combination of frailty syndrome (FS) that severely affect their quality of life. To evaluate the effect of Thera-Band elastic band-assisted progressive resistance-exercise training (PRT) on the physical health of patients with DM complicated by FS, and to provide clinical evidence.</p> Methods <p>Patients with DM complicating FS who received Thera-Band elastic band PRT cases (study group, <i>n</i> = 48), and those who received conventional treatment (control group, <i>n</i> = 48) admitted to Zhejiang Rongjun Hospital from April 2023 to March 2024 were selected for randomized controlled trial (RCT). Blood glucose levels and body function before and after treatment were compared, and patients’ handgrip strength (HS) and usual gait speed (UGS) were measured. In addition, the fatigue, resistance, ambulation, illness, and loss of weight (FRAIL) scale and the Rating of Perceived Exertion (RPE) were used to assess patients’ frailty. Their psychological state was also investigated, and adverse reactions during treatment were counted.</p> Results <p>The research group showed lower blood glucose levels, as well as higher Short Physical Performance Battery (SPPB) scores and levels of HS and UGS than the control group after treatment (<i>P</i> &lt; 0.05). In addition, the frailty status and psychological status of the research group were also demonstrated significant (<i>P</i> &lt; 0.05), while the incidence of adverse reactions was not different from that of the control group (<i>P</i> &gt; 0.05).</p> Conclusion <p>Thera-Band elastic band-assisted PRT may alleviate frailty in DM patients with FS and shows promise for clinical application.</p> Trial registration <p>www.clinicaltrials.gov ID NCT06658106 (Data 21/10/2024).</p>