In this letter, a 3‐D optimized one‐step leapfrog weakly conditional stability finite‐difference time‐domain (WCS‐FDTD) scheme, which introduces the artificial anisotropy parameters into the one‐step leapfrog WCS‐FDTD scheme, is proposed to suppress the numerical dispersion error and boost the accuracy without the enhancement of the simulation complexity. The proposed scheme maintains the property of WCS and stays almost unchanged Courant‐Friedrich‐Levy stability condition as compared to the conventional WCS‐FDTD scheme. The theoretical derivation of the iterative formulation and the analysis of the numerical dispersion are given in detail. The numerical example is presented to demonstrate that the developed scheme has significantly improved the accuracy of the one‐step leapfrog WCS‐FDTD scheme without sacrificing efficiency.