Eutectic behavior and the induced crystalline phase in mixtures of hexagonal columnar liquid crystal, 2, 3, 6, 7, 10, 11-hexakis-(pentyloxy) triphenylene (HPTP)/reactive mesogenic diacrylate monomer, 4-(3-acryloyloxypropyloxy)-benzoic acid 2-methyl-1, 4-phenylene ester (RM257) have been investigated both experimentally and theoretically. To determine the theoretical phase boundaries, we combined the free energy of Flory−Huggins free energy for liquid−liquid demixing, Maier−Saupe free energy of nematic ordering, and Chandrasekhar−Clark free energy of hexagonal ordering. The calculated phase diagram of the HPTP/RM257 blend is essentially of a eutectic type that consists of isotropic (I), nematic (N), and hexagonal columnar (Colh) regions, and nematic + isotropic (N+I), hexagonal columnar + isotropic (Colh+I), and hexagonal columnar + nematic (Colh+N) coexistence regions, bound by the liquidus and solidus lines. Of particular interest is the formation of an induced crystalline phase (Crin) in the intermediate compositions of the HPTP/RM257 mixtures, exhibiting Cr2 (RM257) + Crin in the RM257-rich and Crin + Cr1 (HPTP) in the HPTP-rich regions.