Selective extraction of Mercury(II) using 1‐naphthylthiourea–methyl isobutyl ketone (ANTU‐MIBK) system from hydrochloric acid solutions (0.1–10 M) has been studied. Influence of foreign ions, acid and ligand concentrations has been investigated. Addition of ANTU in MIBK enhanced, extraction capacity of MIBK to several times. Low effect of foreign ions and high separation factors for a number of metal ions determined at 0.5 M hydrochloric acid concentration evaluated the proposed method efficient and selective. The experimental data obtained from application of the method for extraction of mercury from a synthetic aqueous solution reveal that more than 99% mercury can be separated from cadmium, zinc and selenium in a single step with five minutes equilibration.