Ketones are among the most useful functional groups in organic synthesis, and they are commonly encountered in a broad range of compounds with various applications. Herein, we describe the mesoionic carbene‐catalyzed coupling reaction of aldehydes with non‐activated secondary and even primary alkyl halides. This metal‐free method utilizes deprotonated Breslow intermediates derived from mesoionic carbenes (MICs), which act as super electron donors and induce the single‐electron reduction of alkyl halides. This mild coupling reaction has a broad substrate scope and tolerates many functional groups, which allows to prepare a diversity of simple ketones as well as bio‐active molecules by late‐stage functionalization. A metal‐free protocol for the coupling reaction of aldehydes and alkyl halides was successfully developed with mesoionic carbenes (MICs) as catalysts. This versatile strategy delivers a large diversity of simple ketones as well as bio‐active molecules by late‐stage functionalization.