An efficient, operationally simple and one-pot multi-component approach has been developed for the construction of pyrazolyl-thiazoles using sulfamic acid (H₂NSO₃H) as a green catalyst in water. The notable features of this protocol include mild reaction conditions, enhanced selectivity with good yields and wide substrate scope, which makes it an attractive and useful process for the synthesis of biologically important newer pyrazolyl-thiazole compounds. A series of compounds (4a–z) were synthesized and also evaluated for their cytotoxic activity against three human cancer cell lines. Among them, 4b, 4c and 4e exhibited considerable cytotoxicity with an IC₅₀ value of < 5 μM.