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Older adults with type 2 diabetes mellitus (T2DM) are at high risk of polypharmacy and potentially inappropriate medication (PIM) use because of multimorbidity and complex treatment regimens. This systematic review and meta-analysis (PRISMA 2020; PROSPERO CRD420251149348) aimed to estimate the prevalence of polypharmacy and PIM use, describe PIM burden and patterns, and summarize the co-occurrence of PIMs among those with polypharmacy. On 7 September 2025, we searched PubMed, Scopus, Embase, Web of Science, and MEDLINE using a structured search strategy based on the PICO framework. Observational studies of older adults (≥65 years) with T2DM reporting polypharmacy and PIMs were included. Risk of bias was assessed using the JBI checklist, and prevalence estimates were synthesized using a random-effects meta-analysis. Five studies (13,350 participants) were included. Polypharmacy prevalence ranged from 43.6% to 95.3%, while PIM prevalence ranged from 23.4% to 74%. The co-occurrence of PIMs among polypharmacy users ranged from 39.6% to 74%. Commonly reported PIM classes included long-acting sulfonylureas, proton pump inhibitors, and benzodiazepines. Overall, polypharmacy and PIM use were frequently reported among older adults with T2DM; however, the wide variation in prevalence across studies indicates substantial clinical and methodological heterogeneity. These findings highlight the need for structured medication review and clinical context-based medication optimization beyond numerical thresholds.