AbstractThe Pd‐catalyzed conjugate addition of diorganozinc reagents to α,β‐unsaturated carbonyl compounds has been applied to a variety of enone substrates, both cyclic and acyclic, encompassing various combinations of aryl and alkyl substitution, in combination with diorganozinc reagents incorporating alkyl (Me, linear and branched) or Ph groups. While both Pd0 and PdII complexes have been found to be competent precatalysts, reaction yields are strongly dependent on the relative amounts of Pd to phosphane ligand. Thus, a 1:1 Pd/P ratio is well tolerated, but going to Pd/P = 1:2 leads to poor conversions and yields. A calculated Pd0‐mediated pathway involving an unusual oxidative addition step with simultaneous transmetalation, followed by reductive elimination, has been found to be compatible with the observed phosphane effect.