A process for preparing a secondary or tertiary 2-methyl-1,5-pen-tanediamine of the formula I where R1 and R2 are H, C1-C20-alkyl, C3-C8-cycloalkyl, aryl, C7-C20-arylalkyl, where the radicals R1 and R2 may bear substituents selected from the group consisting of C1-C20-alkyl, C1-C20-alkoxy, C6-C20-aryloxy and hydroxy, and R1 and R2 are not simultaneously hydrogen, or R1 and R2 are together an unsubstituted or C1-C20-alkyl- and/or C1-C20-alkoxy-substituted C3-C7-alkylene chain which may, if desired, be interrupted by one or two O or NR3 groups, where R3 is H or C1-C20-alkyl comprises reacting 2-methylglutarodinitrile with a primary or secondary amine of the formula R1R2NH and hydrogen at from 50 to 250° C. and pressures of from 0.5 to 35 MPa in the presence of an oxidic supported catalyst comprising one or more noble metals which has been treated with hydrogen at from 50 to 300° C. for at least 0.5 hour before use. The compound 1,5-bis(dimethylamino)-2-methylpentane is also claimed.