A process for producing an alkoxy-substituted tri-phenylamine comprising reacting an alkoxy-substituted cyclohexanone with a diphenylamine or an aniline, while forming said cyclohexanone in the same system from an alkoxy-substituted phenol by using said phenol as a hydrogen acceptor, in the presence of a hydrogen transfer catalyst and a catalytic amount of the alkoxy-substituted cyclohexanone corresponding to the alkoxy-substituted phenol used for the reaction, or after converting partially the alkoxy-substituted phenol to a catalytic amount of the alkoxy-substituted cyclohexanone under a hydrogen pressure in the presence of a hydrogen transfer catalyst, wherein a surface-supported catalyst is used as the hydrogen transfer catalyst.