Strain-incompatibility accommodation mechanisms in polycrystalline deformation have been examined through a comparative study of experimental octachloropropane deformation and correlated numerical modelling. The results show that potential strain incompatibility between neighbouring grains in a deforming polycrystal can be accommodated by diffusive mass transfer, grain boundary migration, intra-grain inhomogeneous deformation and grain boundary sliding. Diffusive mass transfer is capable of relieving space problems in polycrystalline deformation. This process, together with grain boundary migration, prevented the formation of voids and grain overlaps in the deformed octachloropropane polycrystal. Intra-grain and inter-grain inhomogeneous deformations have a different role in maintaining strain compatibility. The former is sufficient in itself to achieve strain compatibility, whereas the latter causes incompatibility problems. Grain boundary sliding is a process capable of effectively accommodating grain interaction. However, this mechanism causes void formation and does not represent a high strain solution by itself.