Diabetes mellitus remains a global health challenge worldwide and continued therapeutic development of new agents is essential. The pyrimidine derivatives emerged as one of the hopeful candidates and possess diverse pharmacological profiles, targeting central pathways pertinent to diabetes pathogenesis, namely DPP-4 inhibition, α-glucosidase/α-amylase modulation, PPAR-γ agonism, and GLP-1 receptor activation. This review gives a systematic analysis of the structure-activity relationship (SAR) of pyrimidine-based hybrids such as morpholino-triazine, dihydropyrimidine-phthalimide, and quinazolinone-pyrimidine derivatives associated with their higher efficacy, selectivity, and multitarget potential. The mechanistic insights from molecular docking and QSAR studies explain their interaction with different antidiabetic targets and clinical relevance is attributed to anagliptin and tolimidone. New vogue patterns, such as AI-drug designing and conjugate development, are discussed for next-generation therapies. The review covers also the perspectives on challenges, opportunities, and comparative merits over other heterocyclic scaffolds, making these pyrimidine derivatives versatile leads in exploring antidiabetic aspects.