A study is performed on characteristics of lattice dynamics in the initially ordered ternary Ni_{3}(Fe_{1-x}Nb_{x}) (x = O to 10 at.%) alloys using high temperature X-ray diffractometry for the temperature range from 300 K to 1300 K. Aspects investigated included temperature and concentration dependencies of the full mean square atomic displacements Ū²_{f}, the Debye characteristic temperature Θ_{D}, and linear thermal expansion coefficient α. It is found that the Ū²_{f}, Θ_{D}, and α parameters show anomalous change at temperatures where the alloys are subjected to order-disorder phase transitions. It is further found that Nb addition results in the considerable increase in the parameters Ū²_{f} and α and decrease in Θ_{D}. Moreover, the addition of Nb stabilizes Ni_{3}Fe ordered structure and shifts the order-disorder transition to higher temperature.