Growing water scarcity motivates zero liquid discharge. As the final step in many industrial effluents is the crystallization of a saline solution, understanding crystallization of several salts in a single crystallizer is needed to assure their easy separation. In this work, we address the elementary processes in the cocrystallization of NaCl and KCl from aqueous solutions. Process was carried out by batch evaporation of aqueous solutions near the eutectic point seeded with NaCl to minimize its nucleation. When eutectic point is reached, small free single crystals as well as small crystals attached to NaCl crystals surface appear, indicating KCl epitaxial growth on NaCl substrates. Initially large NaCl crystals increase in size by molecular growth mechanism. Simultaneously, more crystals appear and agglomerates of mixed crystals are formed. This study suggests that it may be possible to control the elementary processes involved, by judicious choice of the cocrystallization conditions.