Structure of stacking faults formed in pairs in a ZnSe epitaxial layer grown by gas source molecular beam epitaxy on a GaAs(001) buffer layer was determined with transmission electron microscopy. Extrinsic type stacking faults were formed on (111) and (1¯1¯1) planes with the same polarity, which was determined by convergent‐beam electron diffraction. The two stacking faults meet at a point which is a few atomic layers away from the interface between ZnSe and GaAs. Partial dislocations at the edge of the stacking faults were found to be the Shockley type ones with a Burgers vector of 1/6⟨211⟩. Probable formation processes of the stacking faults have been discussed. ©1995 American Institute of Physics.