A simple one-pot synthesis of vinyl-functionalized MCM-41 (v-MCM-41) is presented. The co-condensation of vinyltriethoxysilane with tetraethoxysilane in an aqueous solution of cetyltrimethylammonium bromide resulted in a vinyl-functionalized, well-ordered hexagonal mesophase. The surfactant could be extracted without affecting the vinyl functionalities. The mesoporous product exhibited a BET surface area of 1424 m2/g. In order to probe the internal pore structure, v-MCM-41 was further functionalized by bromination. Complete bromination of the reactive vinyl groups was possible, implying that all vinyl groups were accessible. A very slow reaction rate indicated that most vinyl groups were present within the mesopore channels. This model reaction demonstrates that v-MCM-41 may be a versatile starting material for many other in-situ reactions resulting in ordered, high surface area materials with specific functional groups.