The interleave boost converter (IBC) has been used as the interface converter between the low-voltage electrical energy sources, such as lithium-ion battery banks, solar panels, and fuel cells, and the dc bus of dc microgrids. With increasing penetration of tightly regulated power electronic loads, which behave as constant power loads, the stability of microgrid dc-bus voltage that is fed by the IBC is threatened by the loads' negative incremental impedance feature. To ensure the stability of the bus voltage, this article proposes a nonlinear disturbance observer (NDO)-based sliding-mode control algorithm. The proposed algorithm has excellent robustness, low computational burden, and no extra hardware cost. A generalized average state-space model is proposed to facilitate the control design. In addition, an NDO is employed to estimate the output power of IBC rapidly and accurately. To verify the effectiveness of the proposed algorithm, simulation and experimental results are presented.