In the quest to improve the understanding the microstructure and properties of laser powder bed fusion manufactured hot work tool steels, this study explores the carbide evolution from the as-built state to the quenched and tempered conditions of a modified H13 steel. The heat treatment included austenitization and quenching followed by two tempering temperatures of 600˚C and 625˚C. To observe the evolution of the primary and secondary carbides with tempering time, different tempering times of 10, 20, 40, 80, 120, 130, 140, 160, 200 and 240 minutes were applied for both temperatures. The samples were investigated with synchrotron based X-ray diffraction, scanning electron microscopy and hardness measurements. Results revealed significant changes in carbide fractions, tetragonality of the martensite, and micro-strain with varying tempering times and temperatures. The study demonstrates the effectiveness of wide angle synchrotron X-ray diffraction in understanding carbide evolution and offers valuable insights for tailoring heat-treatment processes.