The glass-forming ability (GFA), nanocrystallisation, electrical resistivity and soft magnetic properties of (Fe 1-x Co x ) 79 Nb 3 B 18 (x = 0, 0.15, 0.3, 0.45, 0.6, 0.75) glassy alloys were investigated. We found that the substitution of Fe by Co is beneficial for improving the GFA. As-spun (Fe 0.55 Co 0.45 ) 79 Nb 3 B 18 glassy alloys show the best GFA, along with excellent soft magnetic properties in the supercooled liquid region, with a saturation magnetisation and coercivity of 140 A · m 2 · kg -1 and 19.9 A · m -1 , respectively, at 60 K. With increasing Co content, the electrical resistivity initially decreases rapidly, and then fluctuates around approximately 70 ± 4 μΩ cm. With increasing the annealing temperature, the saturation magnetisation improves initially, but then decreases for the (Fe 0.4 Co 0.6 ) 79 Nb 3 B 18 alloy, and the coercivity does not significantly improve. These newly developed FeCoNbB multicomponent alloys exhibit appreciable GFA, good magnetic properties and low material cost, and they can serve as a promising soft magnetic material for use in industrial applications.