Experimental observation of noncritically phase‐matched second‐harmonic generation in a liquid/TiO2/quartz waveguide is reported. The phase‐match condition, approximately independent of waveguide thickness, was achieved by tuning the liquid refractive index. Nonlinear interaction occurs in the quartz between the fundamental (1.06 &mgr;m) TE0mode and the harmonic (0.53 &mgr;m) TM0mode. Mode effective indices were measured versus liquid index to determine the phase‐match point. Coherence lengths greater than 3.5 mm were achieved, but propagation lengths were limited to 4 mm by losses due to surface scattering. These losses arise from waveguide design requirements of noncritical phase matching, not experimental film quality. Conversion efficiency was approximately 0.01%.