This study offers a practical method for converting petroleum sludge (PS) into H 2 ‐rich gas via CO 2 catalytic pyrolysis using activated biochar (ACB) catalysts. Pre‐treatment techniques were applied to prepare phosphoric acid (H 3 PO 4 ; ACB‐P), zinc chloride (ZnCl 2 ; ACB‐Z), and potassium hydroxide (KOH; ACB‐K), which served as catalysts to boost H 2 production through catalytic pyrolysis of PS. The H 2 selectivity showed a rising trend in the subsequent sequence: noncatalytic (non‐C; 6.9 vol%) < raw biochar (7.1 vol%) < ACB‐K (9.7 vol%) < ACB‐Z (17.8 vol%) < ACB‐P (22.9 vol%) at 600°C. These results are attributed to the well‐developed porous structure and abundant acid sites of the ACB catalysts, which promote a carbonium‐ion mechanism. Using ACB‐P yielded higher gas production and H 2 selectivity under CO 2 than under N 2 , emphasizing the important role of catalyst acid sites and CO 2 in the pyrolysis of PS. Additionally, ACB‐P produced more H 2 than commercial charcoal. Increasing the reaction temperature to 700°C improved gas yield, reaching a maximum of 68.2 wt%. Conversely, H 2 selectivity showed an inverse relationship with temperature, decreasing from 48.4 vol% at 500°C to 16.3 vol% at 700°C.