We report on guided-wave second-harmonic generations in nonlinear Nd:YCa4O(BO3)3 (Nd:YCOB) optical waveguides that are produced by the low-fluence swift Ar8+ ion irradiation. The guided-wave second harmonics are realized through the frequency doubling and the self-frequency-doubling of the waveguides under the optical pumps at wavelengths of 1064 and 810 nm, respectively. By virtue of the self-frequency-conversion configuration, the Nd:YCOB waveguides are promising candidates as novel, compact, miniature green laser sources.