Background Patients suffering from diabetic frozen shoulder face particular challenges, including limited shoulder motion and excruciating pain. Although traditional physiotherapy methods are commonly used, it is important to investigate the effectiveness of combining Maitland mobilization with traditional treatments, especially considering patients' tissue irritability levels as often patients cannot tolerate mobilization and exercises due to tissue irritability. This study aimed to investigate the impact of Maitland mobilization combined with a conventional physiotherapy regimen on pain and functional ability using the Visual Analog Scale (VAS) and Disability of the Arm, Shoulder and Hand (DASH) scales in diabetic patients suffering from a frozen shoulder with moderate tissue irritability levels. Methodology A total of 30 diabetic patients suffering from frozen shoulders with moderate irritability levels were assigned to two groups. Group A was administered conventional physiotherapy which consisted of hot moist packs, therapeutic ultrasounds, and exercises. Group B received conventional therapy with Maitland mobilization. The treatment lasted for six weeks with four sessions per week. Pre- and post-treatment pain and disability were assessed using the VAS and DASH scales. Results Post-treatment Groups A and B showed significant improvements. In Group A, the mean VAS score reduced from 4.97 ± 0.26 to 4.00 ± 0.19 (p < 0.001), while Group B showed a greater reduction from 5.00 ± 0.21 to 2.71 ± 0.13 (p < 0.001). Both groups showed an improvement in DASH scores, with the DASH score decreasing from 27.17 ± 2.37 to 21.89 ± 1.89 in Group A (p < 0.001). Group B showed more significant improvement from 27.23 ± 1.73 to 15.12 ± 0.78 (p < 0.001). Intergroup analysis between both groups showed significantly better outcomes in Group B in both VAS and DASH scores (p < 0.001). Conclusions Maitland mobilization with conventional physiotherapy significantly decreases pain and improves functional recovery in diabetic patients suffering from frozen shoulders with moderate tissue irritability levels.