Synthesis and physicochemical characterization of co-crystals of the antiretroviral drug nevirapine (NV) with the pharmaceutically acceptable co-formers saccharin, rac-tartaric acid, maleic acid, glutaric acid and salicylic acid are reported for the first time. The respective stoichiometric NV:co-former ratios are 2:1, 1:1, 1:1, 1:1 and 2:1. In the 1:1 co-crystals, the predicted R22(8) NV(amide)–carboxylic acid supramolecular synthon occurs, whereas in the 2:1 species, the co-former is H-bonded to a centrosymmetric NV dimer formed via the R22(8) amide–amide synthon. Thermal analysis of three co-crystals revealed the unusual phenomenon of precipitation of NV from the melt. Co-crystallization of NV with maleic acid led to the highest (fivefold) increase in the aqueous solubility of the drug.