We present the full magnetic g tensors of the 6H5/2Z1 and 4G5/2A1 electronic states for both crystallographic sites in Sm3+:Y2SiO5, deduced through the use of Raman heterodyne spectroscopy performed along 9 different crystallographic directions. The maximum principle g values were determined to be 0.447 (site 1) and 0.523 (site 2) for the ground state and 2.490 (site 1) and 3.319 (site 2) for the excited state. The determination of these g tensors provide essential spin Hamiltonian parameters that can be utilized in future magnetic and hyperfine studies of Sm3+:Y2SiO5, with applications in quantum information storage and communication devices.