Due to improved efficiency, reduced conversion stages, integration of distributed generators (DGs), and increased use of DC loads, DC microgrids (MGs) are earning extensive approval in modern power grids. Islanding detection is a critical issue for both AC and DC MGs. If the detection technique fails, it may lead to instability in the system, affecting the load-side devices and employees. Therefore, this article aims for the development of a novel passive islanding detection scheme (IDS) based on the cumulative sum of superimposed impedance ( CSOSI ) for DC MGs. In the proposed IDS, voltage and current samples are collected at DGs terminals to analyze a DC MG response for an islanding condition. Superimposed impedance ( SI ) and CSOSI are calculated, and the variations in CSOSI are measured to detect islanding phenomena. The proposed passive IDS is simulated using MATLAB/Simulink environment, and the experimental validation is accomplished on a DC MG hardware setup. The obtained results depict that the proposed technique effectively discriminates islanding events from other nonislanding scenarios and acts effectively during islanding scenarios for radial and ring-type systems irrespective of the type and number of DGs present in the DC MGs. The effectiveness of the proposed scheme is also tested for both constant resistance and constant power loads.