Abstract4‐Bromodiazaphosphole‐3‐oxides or sulfides can be obtained by reaction of the corresponding unsubstituted derivative with appropriate reagents. PTAB was demonstrated to be very regio‐ and stereoselective, allowing bromination exclusively at the 4‐position of the ring with prevalent or exclusive formation of one of the two possible isomers. However, when regioselectivity is not required, cheaper and more available bromine or NBS can be used conveniently. 4‐Chlorodiazaphosphole‐3‐oxides can be obtained by reaction of the corresponding unsubstituted derivative with NCS. 4‐Bromodiazaphosphole‐3‐oxides undergo stereoselective methanolysis as well as parent