In this study, the anisotropic diffusion behavior of Al in hcp Mg was for the first time experimentally investigated using the diffusion couple technique with single crystal Mg at the temperatures ranging between 638 K and 693 K (365 °C and 420 °C). The diffusion coefficients derived from Al profiles in single crystal hcp Mg are D _⊥(a-axis) = 3.1 × 10⁻³ (m²/s) exp(−152154/RT) and D _║(c-axis) = 8.7 × 10⁻³(m²/s) exp(−159221/RT). The diffusion coefficient of Al within the basal plane is about 1.3 times greater than that along normal direction of the basal plane at the experimental temperatures. The interdiffusion coefficients of Mg₁₇Al₁₂ and Mg₂Al₃ solid solutions were also derived, and the values are similar to the previous studies.