© The Royal Society of Chemistry 2016.Epsilon cobalt (?-Co) nanoparticles in a number of octahedral morphologies have been synthesised. The particles are polycrystalline, with sizes in the order of 30 nm. Magnetic studies reveal the particles are ferromagnetic, with a room temperature saturation magnetisation of 131 emu g-1. Unlike other large cubic ?-Co syntheses, we have not added an additional co-surfactant. Instead, we have modified the heating regime and reaction agitation. This alternative method highlights the complex chemistry associated with the formation of cobalt nanoparticles by thermal decomposition.