Solid-state photodecarboxylation occurs in a chiral cocrystal of acridine and diphenylacetic acid to afford a chiral condensation product in modest enantiomeric excess. A chiral cocrystal of 9-methylbenz[c]acridine and diphenylacetic acid also undergoes similar photodecarboxylation but gives an almost racemic product. The different enantioselectivities between the two chiral cocrystals can be understood on the basis of the molecular arrangements in the lattice.