A single-stage gas-phase synthesis of isoprene from formaldehyde and isobutylene in the presence of Al-BEA and Nb-BEA zeolite catalysts containing different amounts of aluminum and niobium has been studied. The physicochemical properties of the catalysts have been studied by low-temperature nitrogen adsorption, infrared spectroscopy of adsorbed CO, X-ray fluorescence analysis, and ammonia TPD methods. Catalytic tests have shown that, at similar formaldehyde conversion values, the isoprene selectivity is higher in the presence of the Al-containing BEA catalysts. It has been found that Al-BEA with Si/Al = 12 exhibits the highest activity in isoprene synthesis.