To address the inherent limitations of conventional magneto-electric dipole antennas, namely their excessive profile height and unidirectional radiation characteristics, this paper presents a planar quasi-Yagi magneto-electric dipole antenna featuring bidirectional end-fire circularly polarized radiation. On the dielectric substrate, two quarter-wavelength shorted cavities are symmetrically arranged in opposite orientations to act as equivalent magnetic dipoles, while metal strips connected in reverse directions at the apertures on both sides of the cavities serve as equivalent electric dipoles. Isotropic directors are incorporated to establish a quasi-Yagi configuration for gain enhancement, and metallized via holes are utilized in place of conventional metallic electric walls to interconnect the upper and lower surfaces of the cavities. Through the parallel arrangement of the equivalent magnetic and electric dipoles, two orthogonal polarization components are generated. The electric dipoles, being connected to the cavity edges, inherently introduce a 90° phase difference, thereby establishing a circularly polarized radiation mode. Simulated results demonstrate that the antenna achieves an overall profile of 0.039λ (where λ denotes the free-space wavelength at the center frequency). At the operating frequency of 5.8 GHz, the reflection coefficient is as low as -39.22 dB, with bidirectional gains of 7.85 dBi in both end-fire directions, axial ratios of 0.71 dB and 0.70 dB, respectively, and a 3-dB axial-ratio bandwidth of 50.17%. By virtue of electromagnetic structure equivalence and parasitic coupling, the proposed antenna attains low-profile, high-purity bidirectional end-fire circularly polarized radiation, rendering it a promising candidate for UAV relay and point-to-point wireless communication applications.