We report on the fabrication of channel waveguides in Nd:YAG crystals, using swift C⁵⁺ ion irradiation with ion energy of 15 MeV and fluence at 5×10¹⁵ ions/cm². A laser-cut shadow mask of a number of open stripes with varied width was covered on the sample surface during the ion irradiation. Channel waveguides were formed in the Nd:YAG crystal due to the refractive index increase along the ion trajectory. Room temperature waveguide laser oscillations at 1064 nm have been observed under 808 nm optical pumping, with laser slope efficiency at 38% and a maximum output power of 36 mW.