In the title compound, C(16)H(25)NO, the N-tert-butyl-propanamide fragment is essentially planar, with the exception of two C atoms of the tert-butyl group (r.m.s. deviation = 0.005 Å), forming a dihedral angle of 84.09 (10)° with the plane of the mesityl fragment (r.m.s. deviation = 0.002 Å). The crystal packing is stabilized by an inter-molecular N-H⋯O hydrogen bond, which links the mol-ecules into chains with graph-set notation C(4) running parallel to the c axis.