The development of a general catalytic system for the palladium-catalyzed carbocyclization of unactivated alkyl bromides with alkenes is described. This approach uses a commercially available bisphosphine ligand and avoids the use of carbon monoxide atmosphere present in prior-studies involving alkyl iodides. Detailed mechanistic studies of the transformation are performed, which are consistent with auto tandem catalysis involving atom-transfer radical cyclization followed by catalytic dehydrohalogenation. These studies also suggest that reactions involving alkyl iodides may proceed through a metal-initiated, rather than metal-catalyzed, radical chain process.