Herein, we introduce a novel method for the synthesis of S‐substituted isothiourea compounds via the selective 1,2‐carboimination between oxime esters as bifunctional reagents and the C=S bond of isothiocyanates under visible‐light catalysis. This approach deviates from conventional methods by precisely modulating the substrate electronics to selectively functionalize the C=S bond of isothiocyanates over the C=N bond, eliminating the need for strong bases and high temperatures and bypassing the formation of thiourea intermediates. Consequently, this protocol enables the efficient one‐step synthesis of S‐alkyl isothioureas, with featuring mild reaction conditions, operational simplicity and broad substrate scope.