In recent years Ni-Mn-Z (Z= Ga, Sn, Sb and In) Heusler alloys have attracted enormous attention owing to their multifunctional properties such as shape memory effect, giant magnetocaloric effect (MCE) and large magnetoresistance, which result from first order martensitic transition from austenite phase to martensite phase [1-3]. Among these properties, MCE is the most prominent as materials showing large MCE near room temperature (RT) are being considered as promising candidates for solid state cooling technology. Magnetic and magnetocaloric properties of these alloys are strongly influenced by Mn-Mn exchange interaction, which can be altered by either chemical substitution or applying pressure. Recently effect of pressure on magnetic and magneto-caloric properties of many Ni rich Ni-Mn-Z alloys have been reported [4-5]. However, no such reports are available on Mn rich Mn-Ni-Z (Z= Ga, Sn and In) Heusler alloys. In present study, we have investigated the effect of hydrostatic pressure on martensitic transition, magnetic and magne-tocaloric properties of Mn rich Mn<inf>50</inf>Ni<inf>41</inf>Sn<inf>9</inf> Heusler alloy. © 2015 IEEE. Krenke, T., Duman, E., Acet, M., Wassermann, E.F., Moya, X., Manosa, L., Planes, A., (2005) Nature Mater., 4, p. 450Du, J., Zheng, Q., Ren, W.J., Feng, W.J., Liu, X.G., Zhang, Z.D., (2007) J. Phys. D: Appl. Phys., 40, p. 5523Barandiaran, J.M., Chernenko, V.A., Lazpita, P., Gutierrez, J., Feuchtwanger, J., (2009) Phys. Rev. B, 80, p. 104404Devarajan, U., Muthu, S.E., Arumugam, S., Singh, S., Barman, S.R., (2013) J. Appl. Phys., 114, p. 053906Nayak, A.K., Suresh, K.G., Nigam, A.K., Coelho, A.A., Gama, S., (2009) J. Appl. Phys., 106, p. 053901Sharma, J., Suresh, K.G., (2014) IEEE Trans. Magn., 50, p. 48004042015 IEEE International Magnetics Conference, INTERMAG 201511 May 2015 through 15 May 2015