[en] Intense 2.9 µm emission corresponding to Dy³⁺:⁶H_13/2 → ⁶H_15/2 transition was achieved in Yb³⁺/Dy³⁺ codoped CaYAlO₄ crystal for the first time. The effects of Yb³⁺ on the spectroscopic properties and energy transfer mechanisms were investigated. In comparison with Dy³⁺ singly-doped CaYAlO₄ crystal, Yb³⁺/Dy³⁺ codoped crystal not only has intense 2.9 µm emission, but also has longer upper laser level lifetime, which facilitates particle number inversion and laser behavior in 2.9 µm. Furthermore, the energy transfer efficiency from Yb³⁺ to Dy³⁺ in Yb³⁺/Dy³⁺ codoped crystal was as high as 87.3%, indicating effective energy transfer of Yb³⁺. Besides, the energy transfer microscopic parameters between Yb³⁺ and Dy³⁺ were theoretically analyzed. The results indicate that the introduction of Yb³⁺ is very beneficial for achieving 2.9 µm laser in Dy³⁺: CaYAlO₄ crystal, which could act as a potential gain media for LD pumped mid-infrared laser.