We studied the effect of dopants (Al, Ti, Zr) on the thermal stability of iron-nitride thin films prepared using a dc magnetron sputtering technique. Structure and magnetic characterization of deposited samples reveal that the thermal stability together with soft magnetic properties of iron-nitride thin films get significantly improved with doping. To understand the observed results, detailed Fe and N self-diffusion measurements were performed. It was observed that N self-diffusion gets suppressed with Al doping, whereas Ti or Zr doping results in somewhat faster N diffusion. On the other hand, Fe self-diffusion seems to get suppressed with any dopant of which the heat of nitride formation is significantly smaller than that of iron nitride. Importantly, it was observed that N self-diffusion plays only a trivial role, as compared to Fe self-diffusion, in affecting the thermal stability of iron-nitride thin films. Based on the obtained results, the effect of dopants on the self-diffusion process is discussed.