Acoustic emission (AE) is employed in this study to understand the failure process in fiber-reinforced cellular concrete (FRCLC) subjected to direct shear load. Synthetic polyolefin fibers are used as reinforcement in FRCLC blocks, and their influence on the shear-fracture process is investigated. AE parameters are investigated to assess the effectiveness of fibers in performance improvement of shear strength and toughness of CLC. In total, 24 CLC specimens are tested under direct shear. Effect of fiber dosage and combinations of macro and microfibers are considered as study parameters. Shear crack bridging effect of fibers during the process of shear-slip is investigated. Test results indicate that AE and shear fracture energy increase with increasing fiber dosage. It is observed that discontinuous structural synthetic fibers significantly improve the ultimate shear strength, residual strength, ductility, stiffness, and toughness of CLC. Also, the structural synthetic fibers reduced the shear crack width and shear-slip of CLC. AE parameters such as counts, energy, and 3D-crack source location are presented to illustrate the role of different fiber dosages on the direct shear response. Shear crack location was found to be consistent with the observed failure planes in the specimens. AE data analysis reveals that the number of mode II type events increased with increasing fiber dosage due to increased fiber pullout. Besides, mode I type events also increased as the failure mode changed from a single split crack to distributed cracking. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.