The local structure and thermal expansion properties of balled-milled manganese nitride fine particles with median diameters on the sub-micrometer scale were investigated. Negative thermal expansion (NTE) properties of the manganese nitrides are noticeably altered even with particle sizes of several micrometers. The present study indicates that the alteration of NTE properties is attributable to the structural disorder resulting from grinding. Moreover, the NTE properties were restored by annealing due to improved structural order. These achievements are expected to pave the way for the use of the giant NTE found in manganese nitrides to control thermal expansion in local regions.