A series of co-crystals of trans-1,2-bis(4-pyridyl) ethylene (bpe) with aliphatic saturated or unsaturated dicarboxylic acids, of the type [(bpe)(L)] (L = dicarboxylic acid), were prepared and characterized by single crystal X-ray crystallography. In all cases chains of the type acid•••bpe•••acid were formed via strong O−H•••N hydrogen bonds. The chains were further linked between them by weak C−H•••O hydrogen bonds, π−π and herringbone interactions to form three-dimensional structures. Thermal analysis showed considerable elevation of the melting/decomposition point of the co-crystals with respect either to both components or to bpe, ascribed to the formation of multiple complementary C−H•••O bonds as well as to π−π interactions between the two conformer molecules. When L = fumaric acid, the two components stack separately with their CC bonds strictly parallel between them at 3.83 Å from one another. However, photodimerization reaction takes place only between the olefin bonds of bpe. Photodimerization reaction between one CC bond of the acid and that of bpe was also induced when L = trans,trans-muconic acid.