Contamination of arsenic in the form of arsenite (As3+) and arsenate (As5+) in potable water causes serious illness in the human body even at a very low concentration (10 µg / L). As3+ is comparatively 60 times more toxic than As5+ species. Hence, this work is focused on the preparation of adsorbents for efficient removal of As3+ with higher adsorption affinity at trace level (≤50 µg/L). Here, iron-doped hydroxyapatite (Fe-HAp) synthesized by hydrothermal technique is employed as an efficient adsorbent. A very less quantity of Fe2+ ion (0.5 wt %) is incorporated in the tetrahedral and octahedral sites of the HAp lattice along the c-axis which lead to drastic reduction in particle size (400%) and enhancing the specific surface area (105%), colloidal stability, and adsorption affinity. The maximum adsorption capacity of As3+ is 139±2 µg/g and 183±2 µg/g for HAp and Fe-HAp, respectively. The adsorption rate of Fe-HAp is very rapid which is 538% higher compared to HAp and also the As3+ adsorption affinity or sensitivity (0.71 µg/L) significantly improved 83-99% when compared to the adsorbents reported in the previous literature so far. The monolayer adsorption of As3+ is purely strong chemisorption as confirmed by the Langmuir and Dubinin–Radushkevich (DKR) isotherm. The structure and morphology of HAp and Fe-HAp remain unchanged after the adsorption of As3+ ions and also no secondary toxic products were observed. Hence, the above results reveal Fe-HAp as an efficient and low-cost adsorbent for removal of highly toxic As3+ ions at the trace level.