Al-doped single-crystalline Si3N4 nanowires were synthesized by catalyst-assisted pyrolysis of polymeric precursors. The doping levels can be controlled by tailoring the Al concentration in the precursors. It is found that the Al concentration has a significant effect on the shape, sizes, and phase compositions of the synthesized Si3N4 low-dimensional nanomaterials. The photoluminescence measurements revealed that the Al dopants have a profound effect on the emission behavior. The current study provides a simple way to realize the controlled doping in Si3N4 nanomaterials, which could be useful for applications in optoelectronic nanodevices.