This paper presents the design of an Adaptive Sliding Mode Controller (ASMC) for a quadcopter operating under external disturbances. Due to the system’s nonlinear and underactuated nature, along with its sensitivity to wind and model uncertainties, achieving stable and accurate flight is challenging. The proposed ASMC combines the robustness of sliding mode control with adaptive laws to handle unknown disturbances and parameter variations in real time. A continuous control law is employed to reduce chattering, while Lyapunov-based analysis ensures system stability. Simulation results demonstrate that the controller enables the quadcopter to track desired trajectories accurately and maintain robust performance under significant disturbances. Compared with conventional methods, the ASMC provides improved tracking accuracy, faster response, and enhanced resilience against external influences. This approach offers a promising solution for reliable quadcopter control in uncertain and dynamic environments.