Pesticide exposure has been implicated as an environmental risk factor for the development of type 2 diabetes mellitus (T2DM). The aim of this study was to investigate the association of the body burden of the pesticide hexachlorocyclohexane (HCH) with the risk of T2DM in a sample of adults from Saudi Arabia. Serum samples were obtained from 280 adult subjects. Hexachlorocyclohexane isomer residues were measured by high-resolution gas chromatography-mass spectrometry. Data on lifestyle, dietary habits, and health status were gathered. Associations between exposure and T2DM were analyzed by logistic regression. Around 49% of adults enrolled in this study were diagnosed with T2DM. Among various HCH isomers, serum concentrations of the pesticides β and γ-HCH were most strongly and consistently linked to T2DM in our studied subjects. Associations of HCH varied across five components of the metabolic syndrome. It positively and significantly associated with four out of the five components, especially elevated triglycerides, high fasting glucose, high blood pressure and HOMA-IR but negatively and significantly with HDL-cholesterol. This study in line with earlier ones about diabetes associated with HCH pesticide exposure and proposes possible hormonal pathways worthy of further investigation.