A series of [FePt]100−xCrx nanoparticles (x=5, 10, and 16at.%) was chemically synthesized by two different techniques. In one method, the simultaneous chemical reduction of FeCl2∙4H2O, Pt-acetylacetonate, and Cr-acetylacetonate was used with 2, 4 hexadecanediol as the reducing agent and phenyl ether as the solvent. The as-prepared particles had a mean size of 1.5nm. In the second method, the simultaneous chemical reduction of Pt-acetylacetonate and Cr-acetylacetonate and the thermal reduction of Fe(CO)5 were used with adamantanecarboxylic acid as the reducing agent and hexadecylamine as the solvent. These as-prepared particles were 3.5nm in size. X-ray diffraction confirmed that the Cr formed a solid solution within the A1 FePt phase for both processes. Upon annealing, the Cr hindered sintered grain growth of FePt nanoparticle arrays. Consequently, we were able to use Cr as a means to tune the ordering temperature as a function of the size effect in FePt nanoparticles. The presence of Cr in the ordered FePt reduced the magnetic coercivity of the transformed nanoparticles.