A physicochemical properties of carbonate-containing zirconium hydroxide T-3K sorbent as well as selective 90Sr sorption from natural waters were studied. It was shown that sorbent consist of ZrO2 (46.39%), Na2O (1.78%) and Al2O3 (1.42%) as the major components in microporous carbonate-containing zirconium hydroxide where sorption of 90Sr occurs due to formation of sparingly soluble strontium carbonate. Affinity of the T-3K sorbent for alkaline earth ions corresponded to the reverse trend of carbonates solubility: Sr > Ba > Ca ≫ Mg and maximum strontium sorption was observed at pH 7–10. Distribution coefficients of strontium were (1.3 ± 0.1) × 103 mL/g for low mineralized water with calcium content of 16 mg/L and 95 mL/g for seawater; static exchange capacity of the sorbent was 30.4 ± 0.5 mg/g.