The first example of second-harmonic generation (SHG) in an ion implanted KTiOPO4 waveguide is reported. This was formed by helium implantation, and SHG was achieved using zero order mode phase matching at λ ζ 1.07 μm. The results indicate that the high nonlinearity remains in the guiding region after implantation. The conversion efficiency in the guide is estimated to be > 10% for ̃ 1 μJ 20 ns pulsed excitation.