Dictyostelium discoideum phenylalanine hydroxylase (DicPAH; residues 1–415) was expressed in Escherichia coli and purified for structural analysis. Apo DicPAH and DicPAH complexed with dihydrobiopterin (BH2) and FeIII were crystallized using 0.06 M PIPES pH 7.0, 26%(w/v) PEG 2000 by the hanging‐drop vapour‐diffusion method. Crystals of apo DicPAH and the DicPAH–BH2–FeIII complex diffracted to 2.6 and 2.07 Å resolution, respectively, and belonged to space group P21, with unit‐cell parameters a = 70.02, b = 85.43, c = 74.86 Å, β = 110.12° and a = 70.97, b = 85.33, c = 74.89 Å, β = 110.23°, respectively. There were two molecules in the asymmetric unit. The structure of DicPAH has been solved by molecular replacement.