Magnetic properties of the single-crystalline Lu 2 Fe 17−x Mn x compounds, in which x=0, 0.5, and 2, with the Th 2 Ni 17 -type crystal structure are reported. The Lu 2 Fe 17−x Mn x compounds with x=0 and 0.5 are ferromagnets at low temperatures and antiferromagnets at high temperatures. The compound with x=2 is always a ferromagnet. The easy-plane magnetic anisotropy in the Lu 2 Fe 17−x Mn x ferromagnets drastically weakens with increase in Mn content up to x=2. The temperature dependence of the first magnetic anisotropy constant was obtained and compared with the single-ion model prediction.