During crystallization experiments two new polymorphs of the highly-active organic nonlinear optical (NLO) material 3-methyl-4-methoxy-4′- nitrostilbene (MMONS) have been discovered. Crystallization conditions of all three polymorphs and their characterization via crystal structure determination from single crystal X-ray diffraction data at 100 K have been discussed in detail. Two of the polymorphs exhibit different conformations, while a third polymorph incorporates both conformers as well as disorder. Comparisons between various types of intermolecular contacts in these three polymorphic forms have been quantified via Hirshfeld surface analysis. © The Royal Society of Chemistry.