A method for producing cladribine (2-chloro-2′ deoxyadenosine) comprising the steps of: a) reaction of 2-deoxyuridine with 2-chloroadenine, in the presence of uridine phosphorylase (UPase) and purine nucleoside phosphorylase (PNPase) in an aqueous reaction medium possibly containing up to 40% v/v of an aprotic dipolar solvent, to obtain cladribine dissolved in said reaction medium; b) isolation of the cladribine by precipitation by means of concentration and alkalinisation of the reaction medium up to pH 11.5-12.5.