In this work, a compact phoswich detector consisting of a cylindrical LaBr₃(Ce) principal crystal and a well-shaped CsI(Tl) sub-crystal was designed and assembled to identify and reject Compton scattering in the LaBr₃(Ce). Two different crystals coupled to the same photomultiplier tube (PMT). The energy deposition in each layer from incident radiation is then determined via digital pulse shape analysis of the PMT’s pulses. The results of Geant4 simulations were used to verify the performance of the pulse shape identification and the effect of Compton background suppression. Experimental tests were conducted on the detector prototype using a ⁶⁰Co gamma source, and the result shown that the detector background suppression coefficient was 2.33(1) which achieved the expected purpose of twice as much as the Compton background was suppressed.