In the title compound, C21H22N2O, the planes of the two six-membered rings make a dihedral angle of 89.51 (7)°. The pyrrolidine ring has a puckering amplitude q 2 = 0.418 (3) and a pseudo-rotation phase angle ϕ2 = -166.8 (5), adopting a twist conformation (T). The other five-membered ring has a puckering amplitude q 2 = 0.247 (2) and a pseudo-rotation phase angle ϕ2 = -173.7 (5), adopting an envelope conformation with the CH2 atom adjacent to the C atom common with the pyrrolidine ring as the flap. In the crystal, mol-ecules are linked via C-H⋯N, enclosing R (2) 2(20) rings, forming chains propagating along [100]. The aceto-nitrile group is disordered over two positions and was refined with a fixed occupancy ratio of 0.56:0.44.