We report on the synthesis of ferromagnetic manganese arsenide (MnAs) nanoparticles viathe conversion of primary Mn particles which are generated in an aerosol process in a sparkdischarge generator. After sintering and size selection in an aerosol setup, the particles aredeposited on GaAs(100)B and Si(111) substrates. Subsequent conversion to MnAsparticles takes place in an annealing process under a hydrogen atmosphere with anarsine background pressure. The magnetic properties are studied using a SQUIDmagnetometer. The annealed MnAs particles exhibit hexagonal facets and showanisotropic magnetic behaviour on GaAs(100)B substrates, whereas on Si(111) theyremain spherical and show isotropic magnetic behaviour. Scanning transmissionelectron microscopy studies are used to confirm the conversion from Mn to MnAs.