The magnetic transition has been studied in Mn1.1Fe0.9P0.8Ge0.2 by magnetic measurements and 57Fe Mössbauer spectroscopy. The alloy crystallizes in the hexagonal Fe2P-type structure with lattice constants of a=6.0476(4) Å and c=3.4766(7) Å. Both bulk magnetization measurements and Mössbauer spectroscopy show that the as-prepared sample has a significantly lower transition temperature on first cooling (TC1≈200 K) than after it has undergone thermal cycling to 20 K (TC20 K=240 K). The behavior of the material stabilizes after the first cooling/heating cycle and no further changes are observed in TC. Working with a stabilized sample, we find that the temperature dependence of the hyperfine field, Bhf(T), is more rapid than that predicted by a simple mean field Brillouin function, and in addition, Bhf(T) shows a thermal hysteresis of 10 K upon cooling versus heating. These results show that the magnetic transition at TC is definitely first order and suggest that there is an additional irreversible magnetostructural change during the first cooling process of the as-prepared sample.