Thioredoxin reductases are homodimeric flavoenzymes that catalyze the transfer of electrons from NADPH to oxidized thioredoxin substrate. Bacterial thioredoxin reductases represent a promising target for the development of new antibiotics. Recombinant thioredoxin reductase TrxB from Streptomyces coelicolor was crystallized using the hanging‐drop vapour‐diffusion method. X‐ray diffraction data were collected from cryocooled crystals to 2.4 Å resolution using a synchrotron‐radiation source. The crystals belonged to the primitive monoclinic space group P21, with unit‐cell parameters a = 82.9, b = 60.6, c = 135.4 Å, α = γ = 90.0, β = 96.5°.