In contrast to recent significant progress in the development of catalytic methodologies for nitrogen acylations, syntheses of N-acyl sulfoximines have been slow to evolve, and still largely rely on the use of stoichiometric amounts of activating reagents. Here we describe the direct acylation of the nitrogen atom in sulfoximines with carboxylic acids promoted by a heterocyclic catalyst featuring the B3NO2 ring system. The protocol used was found to be operationally simple and to tolerate a wide range of functional groups, furnishing the N-acylated sulfoximines in good yield. The multiboron catalyst tamed previously intractable nitrogen nucleophiles, allowing for the short synthesis of a factor Xa inhibitor by catalyzing two consecutive nitrogen acylations in the same pot.