The purpose of this paper is to explore the appli- cability of linear time-invariant (LTI) dynamical systems with polytopic uncertainty for modeling and control of islanded DC microgrids under plug-and-play (PnP) functionality of distributed generations (DGs). We develop a robust decentralized voltage control framework to ensure robust stability and re- liable operation for islanded DC microgrids. The problem of voltage control of islanded DC microrgids with PnP operation of DGs is formulated as a convex optimization problem with structural constraints on some decision variables. The proposed control scheme offers several advantages including decentralized voltage control with no communication link, transient stabil- ity/performance, plug-and-play capability, scalability of design, applicability to microgrids with general topology, and robustness to microgrid uncertainties. The effectiveness of the proposed control approach is evaluated through simulation studies carried out in MATLAB/SimPowerSystems Toolbox.