Fexinidazole is prepared according to a method which comprises the following steps: a) reacting 1-methyl-2-hydroxymethyl-5-nitro-imidazole with methanesulfonyl chloride in the presence of a suspension of powdered alkaline carbonate in an anhydrous organic solvent suitable for performing nucleophile substitution reactions; b) adding to the resulting reaction medium a solution of 4-methyl-mercapto-phenol in the same organic solvent as referred to in step a); c) separating fexinidazole from the reaction mixture as its hydrochloride salt and d) converting said hydrochloride salt into fexinidazole and optionally, purifying the latter.