Production of higher carboxylic acids from CO₂ and H₂ is a novel and very attractive topic. Herein we present a protocol of synthesizing C₃₊ carboxylic acids via the reaction of alcohols with CO₂ and H₂. A catalytic system consisting of iridium(III) acetate and LiI could effectively accelerate this reaction. The reaction could occur at above 120 째C and the best result was obtained at 170 째C. The catalytic system could be applied to various alcohols (primary, secondary, and tertiary alcohols and polyols). The reaction mechanism was proposed based on systematic control experiments.