Background: Diabetes mellitus (DM) and shoulder stiffness (SS) are related. Pain and limitations in both active and passive ROM are its defining characteristics. SS is caused by a fibrotic process, just like other diabetic problems (such as arterial stiffness, pancreatic or renal fibrosis). One of the most popular osteopathic manual treatment techniques for shoulder issues is the Spencer muscular energy technique (MET). Objective: This research assessed the impact of Spencer MET on stiff shoulder in diabetic patients. Patients and Methods: 30 female diabetic frozen shoulder (FS) patients, equally split into two groups; group (A) received Spencer MET along with conventional treatment, while group (B) received conventional treatment only. Patients were recruited from Agouza Police Hospital outpatient clinics. Pain and shoulder range of motion were assessed for all participants, outcomes included pain using numeric pain rating scale (NPRS), pain pressure threshold (PPT) while shoulder range of motion assessed by using standardised manual goniometer and shoulder pain and disability index (SPADI). Results: Post 8 weeks of intervention, group A had a significant lowering in NPRS by 1.73±0.25 contrasted to the control group 4.13±0.92 and increase PPT by 8.73±0.96 contrasted to the control group 7.07±0.8. The study group had a significant reduction in SPADI score by 32.07±5.36 points compared to the control group by 45.93±6 points. Furthermore, the study group showed a significantly increase in Shoulder flexion ROM by 156.33±11.87 points than the control group by 128.67±10.36 points, Shoulder abduction ROM by 127.33±11.6 points than the control group by 104±11.54 points, Shoulder external rotation ROM by 68.33±6.17 points than the control group by 55.33±4.42 points. Conclusion: The Spencer MET along with conventional treatment is more effective decreasing pain and increasing functional ability in patients with stiff shoulder as compared to conventional treatment alone.