alpha-Trifluoromethyl-styrenes, trifluoromethyl-enynes, and dienes undergo palladium-catalyzed trimethylenemethane cycloadditions under mild reaction conditions. The trifluoromethyl group serves as a unique a-electron-withdrawing group for the activation of the olefin toward the cycloaddition. This method allows for the formation of exomethylene cyclopentanes bearing a quaternary center substituted by the trifluoromethyl group, compounds of interest for the pharmaceutical, agro-chemical, and materials industries. In the diene series, the cydoaddition operates in a [3 + 4] and/or [3 + 2] manner to give rise to seven-and/or five-membered rings. This transformation greatly improves the scope of the TMM cydoaddition technology and provides invaluable insights into the reaction mechanism.