To address sustainability issues, the green synthesis of nanomaterials has recently received considerable attention. This article addresses a novel and cost‐effective adsorbent for the extraction of eight phenyl‐N‐methylcarbamate insecticides from water samples. We first synthesized a magnetite/hydroxyapatite nanocomposite using snail shell powder via an environmental friendly approach. The morphology and physicochemical properties of magnetic hydroxyapatite were characterized by Fourier transform infrared spectroscopy, energy‐dispersive X‐ray spectroscopy, and scanning electron microscopy. Magnetic extraction parameters were optimized using a Doehlert matrix. Under optimum conditions, the magnetic extraction coupled with a LC–MS method shows good linearity with R2 ≥ 0.9982, suitable intra‐ and interday precision, and limits of detection and quantification in the range of 0.052–0.093 μg/L and 0.11–0.31 μg/L, respectively. Satisfactory relative recoveries of all carbamates were achieved from fortified water samples in the range of 93.89–101.01%.