The one-step vertical alignment of liquid crystals (LCs) was achieved by forming a novel self-assembled molecular layer of alkylated benzoic acid derivatives on an indium tin oxide substrate through hydrogen bonding. This method utilizes the simple doping of the alignment material into the LCs. The assembled molecular layer promoted the stable homeotropic LC alignment. The electro-optical characteristics of LC devices exhibited stable vertical alignments and fast response times, depending on the number of rigid aromatic rings in the alignment material. Our simplified alignment method allows the fabrication of LC devices without a separate alignment step for fast LC switching.