X-ray powder diffraction data, unit-cell parameters, and space group for ruxolitinib are reported [a = 8.7211(5) Å, b = 19.6157(15) Å, c = 18.9645(10) Å, β = 90.903(6)°, unit-cell volume V = 3243.85 Å3, Z = 8, and space group P21]. All measured lines were indexed and are consistent with the corresponding space group. No detectable impurities were observed. The single-crystal data of ruxolitinib are also reported [space group P21, a = 8.7110(2) Å, b = 19.5857(4) Å, c = 18.9372(4) Å, β = 90.8570(10)°, unit-cell volume V = 3230.53(10) Å3, Z = 8]. The experimental powder diffraction pattern has been well matched with the simulated pattern derived from the single-crystal data.