The study compares the growth, yield, and proximate composition of Amaranthus hybridus, Amaranthus cruentus, and Amaranthus deflexus, grown with poultry manure and NPK in relation to the unfertilized soil of Ilorin, Nigeria. Viable seeds of the Amaranths raised in nursery for two weeks were transplanted (one plant per pot) into unfertilized soil (control) and soils fertilized with either NPK or poultry manure (PM) at 30 Kg ha⁻¹ rate arranged in randomized complete block design with four replicates. Data were collected on plant height, stem girth, number of leaves, leaf area, and number of branches from 1 week after transplanting (1 WAT). Fresh weight, dry weight, and proximate composition were determined at 6 WAT. Except for the length, breadth, and number of leaves, the order of growth parameters and yield in the three Amaranthus species was NPK > PM > control. NPK grown Amaranthus species had the highest protein while PM‐grown vegetables had the highest ash content. Crude fibre in A. cruentus grown with PM was significantly higher than NPK and the control. The NPK treatment of A. hybridus and A. deflexus had the highest crude fibre content. NPK and PM favoured growth and yield of the Amaranthus species but influenced proximate composition differently.