The direct and enantioselective γ alkylation of α-substituted α,β-unsaturated aldehydes under dienamine catalysis has been achieved. A cooperative catalysis system that involves dienamine activation of α-branched enals and chiral Brønsted acid catalysis promotes an SN1-alkylation pathway while ensuring complete γ-site selectivity and high stereocontrol (see scheme; Bn = benzyl).