We present magnetic and transmission electron microscopy experiments on the double-exchange compound La_2/3Sr_1/3MnO₃, nanostructured to form tubes with 700 nm of external diameter. Microscopy reveals that their walls are formed by a compact agglomerate of grains, whose sizes are around 20 nm. The study of magnetic properties of randomly oriented nanotubes shows that the transition from the ferromagnetic to paramagnetic state is at T_C = 320 K, close to the bulk sample value. They exhibit hysteresis in magnetic field loops. The coercive field at 90 K is around 130 Oe, and estimated single-domain size is around 20 nm.