We propose and experimentally demonstrate a bidirectional angled multimode interferometer (Bi-AMMI) for interleaved wavelength division multiplexing applications. The spectral response of the 2 × 4 Bi-AMMI is obtained using an eigenmode expansion method, including the cross coupling between the input and output ports at the same side of the multimode waveguide. To verify our design, both the standalone and interleaved Bi-AMMIs were fabricated and measured. The Bi-AMMI exhibits an insertion loss of 0.99 to 1.21 dB, and the unwanted cross coupling is lower than −20 dB. The interleaved device exhibits a measured optical loss of 4.77 to 5.02 dB, and the average crosstalk is calculated to be −18 dB.