Glass forming ability (GFA), magnetic properties and the microstructure of an Nd60Al20Fe20 as-cast rod were investigated in comparison with as-spun ribbons. The as-cast rod with a diameter of 3 mm and as-spun ribbons exhibit typical amorphous characters in x-ray diffraction patterns and distinct glass transition in differential scanning calorimetry traces. However, glass transition, crystallization behaviours and magnetic properties of an as-cast rod are different from that of as-spun ribbons. Microstructural investigations have revealed that a few nano-crystalline particles are embedded randomly in an amorphous matrix of the as-cast rod while the as-spun ribbons are fully amorphous. The formation of these nano-crystalline particles with a structure and composition similar to the Ax phase, as well as its effect on the magnetic properties and apparent GFA of Nd60Al20Fe20 glass forming alloys, were investigated.