Lattice parameter, particle size, and thermal expansion results obtained from high-temperature synchrotron transmission X-ray diffraction are reported for magnetostructual NiAs-type MnBi nanorods embedded in a Bi matrix. The structural data are consistent with elevated-temperature magnetic measurements that indicate a first-order nanorod Curie transition at 520 K, significantly depressed from the bulk MnBi Curie temperature of 633 K. The data suggest that the unit cell volume dependence of the magnetic behavior-also known as the volume exchange striction-of the MnBi compound is the determining factor underlying this phenomenonon. The results imply that materials with magnetostructural transitions of technological interest may be altered by strain effects to tailor the interatomic distances towards the critical transition values.