Butafulvene, a cyclobutene skeleton bearing two exocyclic conjugated methylene units, demonstrates anti-aromaticity and the intrinsic high strain energy although it is a constitutional isomer of benzene. The preparation of butafulvenes has been a fundamental issue for the development of butafulvene chemistry. Herein, an efficient palladium-catalyzed coupling protocol involving propargylic compounds has been developed to provide a solid and versatile strategy for the rapid assembly of symmetric butafulvene derivatives. Based on the mechanistic studies, two complementary mechanisms, both involving Pd-catalysis, have been confirmed. With the mechanism unveiled, synthesis of unsymmetric butafulvenes has also been achieved. The reaction enjoys the tolerance to a wide range of propargylic molecules, mild conditions, simple catalytic systems, and easy scalability. The synthetic potentials of the products as platform molecules for cyclobutene derivatives have been demonstrated. (Accepted by Nat. Chem.)