A coarse-wavelength-division multiplexer (CWDM) chip, based on grating-assisted contra-directional couplers, was designed, fabricated, and experimentally characterized. The device integrates three gratings, with distinct reflection wavelengths, in a cascaded configuration. The grating-assisted contra-directional coupler structure eliminates the need for discrete circulators as well as effectively mitigates the additional 6-dB loss typically associated with traditional on-chip beam splitters. Furthermore, this design remarkably suppresses crosstalk between the reflected light and output signal. Leveraging a silicon-on-insulator platform, key parameters such as grating width and the number of periods were optimized, and an apodization design methodology was adopted for performance enhancement. Consequently, a compact three-channel CWDM chip was successfully fabricated. Experimental measurements indicate that the on-chip insertion loss and channel crosstalk are approximately 2.5 dB and below −24 dB, respectively, and the spectral response is characterized by a box-like shape. The chip occupies an area of merely 0.6 mm × 1.5 mm. This study addresses the critical technical challenges related to large device dimensions, narrow bandwidths, and the realization of box-like spectral responses in conventional CWDM devices. The developed chip is promising for metropolitan access networks, fiber-to-the-home systems, data center interconnections, and silicon-based photonic integrated circuits.