The optical waveguides in neodymium-doped gadolinium gallium garnet crystal are fabricated, to our knowledge for the first time, by either ${\mathrm{H}}^{+}$ or ${\mathrm{C}}^{3+}$ ion implantation. The reconstructed refractive index profiles of the planar waveguides have shown, in both cases, the typical $“\text{enhanced well}”+“\text{barrier}”$ distributions. The two-dimensional modal profiles of the channel waveguides, obtained by using an end-face coupling arrangement, are in good agreement with the simulated modal distributions. After moderate thermal annealing at $200°\mathrm{C}$ , the propagation loss of the H- and C-ion-implanted channel waveguides are reduced down to $\sim 1.5$ and $\sim 1.6\mathrm{dB}/\mathrm{cm}$ , respectively, which exhibits acceptable guiding qualities for applications on potential integrated laser generation.