Racemic (2Z,4E)-4-[3',4'-dihydro-1'(2'H)-naphthalene-r-ylidene]-2-butenoic acid (1) is a polyene chain-shortened analog of (9Z)-retinoic acid (3) which uses a tetrahydronaphthyl ring to conformationally constrain the C6-C7 single bond (retinoic acid numbering). The structure of (1) was obtained to determine the effects of the tetrahydronaphthyl ring on the ring to polyene chain conformation as compared to a published crystal structure for (9Z)-retinal (2). The results reveal significant differences between the solid state structures of (1) and (2), particularly for torsion angles about C6, C7 and C8, C9. The title compound crystallizes in the centrosymmetric monoclinic space group P21/n with Z = 4. (Cell dimensions: a = 10.863(2) Å, b = 7.637(2) Å, c = 15.781(3) and β = 106.11(3)°.) The structure was refined to R = 3.88% for those 1132 unique data with |Fo| > 6σ(Fo). In the crystal structure, the molecules adopt a hydrogen bonded dimeric structure.