The effect of temperature on the microstructural stability and mechanical properties of ordered ellipsoidal B2-NiAl nanoprecipitates in a novel body-centered-cubic (BCC)-based Fe_3.5Cr_1.5NiA_l0.8 multicomponent alloy (MCA) was investigated. XRD, EBSD, EPMA and TEM were used to characterize the microstructure and phase composition of this MCA. The results showed that the designed coherent microstructure with a high-content ellipsoidal B2 nanoprecipitates in BCC matrix could be maintained up to a high temperature of 1073 K with an average particle size of 245.509-251.328 nm. The unique coherent structure of the as-cast and heat-treated (873 K ≤ T ≤ 1073 K) alloys could be designed to provide a high yield strength (809.2-1164.1 MPa) owing to the low-misfit coherent precipitation strengthening mechanism. When heat treatment temperature was further increased (1173 K ≤ T ≤ 1273 K), the mean particle size of the B2 nanoprecipitates gradually coarsened, and the load transfer strengthening mechanism played a major role in improving the yield strength.