It is well known that the laser crystal with mid-infrared (MIR) broadened and enhanced luminescence is of great significance for various applications, such as atmospheric monitoring, medical surgery and compact, and efficient coherent sources. Herein, we exploit the sensitization and deactivation effects of Yb/Dy ions to achieve broadening and enhancement ~3 μm emission of Er: I→I transition in Yb/Er/Dy: PbF crystal. The energy transfer (ET) mechanism between Yb, Er, and Dy was studied. A broadened and enhanced emission with a full width at half maximum of 265 nm was obtained at ~3 μm due to the fact that Er and Dy ions were used as the emission center at the same time. On the one hand, the incorporation of Dy ion can solve the self-termination bottleneck effect of Er ion, reducing the lifetime of Er: I level. On the other hand, Dy ion can simultaneously serve as the emission center of 3 μm, broadening and enhancing the emission of 3 μm. The experiments show that the corresponding ET efficiency Er: I→Dy: H level is as high as 98.0%, indicating that Dy ion can be used as an effective deactivating ion, benefitting to achieve broadening and enhancing MIR emission around 3 μm. Hence, the Yb/Er/Dy: PbF crystal is an attractive laser medium for MIR broadband tunable laser applications.