The ongoing energy crisis has made it imperative to develop low-cost, easily fabricated, yet efficient materials. It is highly desirable for these nanomaterials to function effectively in multiple applications. Among transition metal dichalcogenides, tungsten diselenide (WSe2) shows great promise but remains understudied. In this work, we doped WSe2 with Mn using a simple hydrothermal method. The resulting material exhibited excellent electrocatalytic activity for the hydrogen evolution reaction, achieving a low overpotential of -0.28 V vs. RHE at -10 mA cm-2, enhanced conductivity, and high stability and durability. Moreover, as an anode material in lithium-ion batteries, the Mn-doped WSe2 outperformed pristine WSe2, reaching initial discharge capacities of 1223 and 922 mA h g-1, respectively. Additionally, the Mn-doped material maintained a significantly higher discharge capacity of 201 mA h g-1 compared to intact WSe2, which had 68 mA h g-1 after 150 cycles. This work offers novel insights into designing efficient bifunctional nanomaterials using transition metal dichalcogenides.