Abstract: A process for producing an ether and an olefin from a hydrocarbon cut containing at least one tertiary olefin, by synthesis of at least one tertiary alkyl ether then fractionation to recover an organic fraction containing the ether which is decomposed into a product (P1) containing at least one alcohol and at least one tertiary olefin, which is fractionated, then the tertiary olefin is purified in a water washing extraction zone (L1) from which a fraction containing the tertiary olefin is recovered and sent to a separation zone (Co) from which an aqueous liquid fraction and a liquid hydrocarbon fraction containing the major portion of the tertiary olefin are recovered.