© Published under licence by IOP Publishing Ltd. Fe2MnSi exhibits a ferromagnetic transition at TC and another transition to a phase with antiferromagnetic components at a low temperature of TA . By substituting V for Mn, so as to obtain Fe2Mn1-xV x Si, TA decreases with x and then vanishes around x ∼ 0.2. In this study, the magnetic transitions are investigated by magnetization measurements for Fe2Mn1-xV x Si (y = 1, 0 ≤ x ≤ 0.2) in high magnetic fields up to ∼70 T and for Fe1.5(Mn1-xV x )1.5Si (y = 1.5, 0 ≤ x ≤ 0.1) up to 5 T. For y = 1.5, with increasing x, TC increases and TA decreases as for y = 1, and the rate of the decrease in TA with x is slightly smaller than for y=1. In the low magnetic field region, TA for y = 1 does not significantly change due to the magnetic field but a distinct decrease is observed in high fields. The critical field at 0 K of this transition in Fe2MnSi is found to be larger than 70 T, and with increasing x, the critical field decreases corresponding to the decrease of TA at zero field.