The antiferromagnetic order in the cubic heavy-fermion compound CeIn_3-xSn_x can be suppressed by Sn doping until a quantum critical point is reached at x_c = 0.67. Thermodynamic measurements indicate changes to the simple magnetic order for x > 0.2, which is corroborated by the fact that neutron scattering experiments failed in observing signatures of the magnetic order for x > 0. We performed muon spin relaxation measurements in zero magnetic field (ZF-μSR) on single crystals of CeIn_3-xSn_x with x = 0.2; 0.4; 0.55. The spectra for x = 0.2 can be fitted by a Gaussian Kubo-Toyabe function with exponential depolarization, whereas the damping in the case of x = 0.55 has Lorentzian shape. The data for x = 0.4 are represented best by a superposition of Gaussian and Lorentzian damping. For all investigated Sn concentrations the muon spin depolarization rate is high at low temperatures and decreases towards T_N. Our measurements demonstrate that magnetic order is present in CeIn_3-xSn_x also for higher Sn content (x ≥ 0.2) and that the distribution of internal fields broadens with increasing x.