Abstract In this work, we synthesized a series of metal‐substituted potassium heteropolyacid salts and investigated its catalytic activity on oxidation of benzyl alcohol with H 2 O 2 under homogeneous (CH 3 CN) and biphasic (toluene/water) conditions. The Keggin heteropolyacids were converted to lacunar salts (i. e., K 7 PW 11 O 39 ; K 7 PMo 11 O 39 and K 8 SiW 11 O 39 ), which had their vacancies filled with metal cations (i. e., Al 3+ , Fe 3+ , Co 2+ , Cu 2+ , and Ni 2+ ), generating the metal‐substituted salts. The K 5 PW 11 NiO 39 proved to be the most efficient catalyst. The synergic effect raised between the PW 11 O 39 7− anion and Ni 2+ cation improved the redox properties and the activity of the catalyst. The K 5 PW 11 NiO 39 catalyst was able to promote the benzyl alcohol oxidation with hydrogen peroxide in biphasic conditions in the absence of phase transfer catalyst. Benzaldehyde and benzoic acid were the main products. The effects of main reaction parameters were assessed. The K 5 PW 11 NiO 39 catalyst was successfully recovered and reused without losing activity.