Abstract A series of O-triorganosilyl selenocarboxylates 2 are prepared by the reaction of sodium or potassium selenocarboxylate 1 with triorganosilyl chlorides. The selenone esters 2 are stable towards heat, but labile towards moisture, and are formed via Se-triorganosilyl selenocarboxylate 3. In the mass spectrometer, isomerization of 2 to its less stable selenol ester 3 takes place, resembling the Schönberg thione-thiol rearrangement.