Diabetes mellitus and depression are closely associated chronic disorders that together impose a substantial burden on individual health and healthcare systems, particularly in developing countries. The bidirectional relationship between metabolic dysregulation and neuropsychological stress indicates that there are therapeutic strategies that can address both conditions simultaneously. Polyherbal formulations are increasingly explored as alternative interventions due to their multi-targeted mechanisms, synergistic pharmacological effects, and comparatively lower risk of adverse reactions than synthetic drugs. In the present study, a polyherbal extract (PHE) was formulated using Aegle marmelos, Prosopis cineraria, and Linum usitatissimum, plants traditionally recognised for their antidiabetic, antioxidant, and neuroprotective properties. Extraction was carried out using Soxhlet extraction with ethanol at 50°C, along with mucilage preparation techniques. The formulated extract was evaluated for physicochemical parameters, including moisture content, ash values, and foreign matter, followed by qualitative phytochemical screening to identify major bioactive constituents. Cytotoxicity and preliminary safety were assessed using the MTT assay on cultured cells. Phytochemical analysis confirmed the presence of flavonoids, alkaloids, terpenoids, tannins, steroids, carbohydrates, and glycosides, indicating a diverse bioactive profile. Physicochemical evaluation demonstrated acceptable stability, with moisture content ranging from 7.49 to 8.67%, ash values between 10.53 and 12.23%, and foreign matter below 1.1%. The MTT assay revealed an IC₅₀ value of approximately 212 µg/ml, with more than 80% cell viability observed at 100 µg/ml, suggesting low cytotoxicity at therapeutically relevant concentrations. Overall, the findings indicate that the formulated polyherbal extract possesses favourable stability, safety, and phytochemical characteristics, supporting its potential application in the management of diabetes-associated depression. Further in vivo studies and bioanalytical investigations are necessary to validate its therapeutic efficacy and elucidate underlying mechanisms of action.