Radical crosslinking reactions utilizing vinyl functionality are widely used to fabricate polymeric networks for bulk and surface applications. Here, we report a thermally latent vinyl crosslinking of polymers involving sulfoxide chemistry for the first time. Polymers with sulfoxide-protected methacrylate moieties are prepared via free-radical polymerization. These moieties are deprotected by a thermal process and transformed into methacrylate functional groups. The crosslinking behaviors of the protected polymers are investigated using an oscillatory rheometer in the presence of a radical initiator. The behavior strongly depended on the formation of methacrylate species in polymer chains. The thermally latent crosslinking approach introduces a novel method for the stepwise and systematic construction of polymeric networks that can potentially be applied in dual-curing or patterning processes.