Undoped GaSb epilayers were grown on GaSb and GaAs substrates using the metalorganic chemical vapor deposition (MOCVD) technique, and photoluminescence (PL). Hall effect measurements were used to characterize the undoped epilayers. For undoped GaSb epilayers, four energy levels revealed by PL spectra are shown to be due to acceptors, usingKTdp/dEfvaEf‐Evdata obtained from Hall effect results, wherepis the hole concentration,EfandEvare the Fermi level and the top of valence band, respectively. The acceptor levels lie at 3, 58, 80, and 130 meV above the top of valence band, respectively. The donor level is 15 meV below the bottom of the conduction band. These acceptor levels exist in almost all of the undopedp‐type GaSb epilayers grown at high temperature, while the donor level exists only in the undopedn‐type GaSb epilayers grown by low‐temperature MOCVD. It is found that these levels may be changed using the different growth temperatures.