We report the first demonstration of narrowband (<17 A˚ full width at half maximum) wavelength selective grating‐assisted coupling between vertically stacked buried rib InGaAsP/InP channel waveguides. These vertically coupled channel waveguides form the basis both of integrable filters essential to photonic circuits such as amplifier/filter and demultiplexer/detector circuits as well as a general approach to vertical integration of photonic circuits.