A flexible dust cover is provided for use with a parallel optical communications module for preventing airborne matter, such as dirt, dust, and gases from entering the module. The flexible dust cover fits snugly to the module to protect components of the module and the optical pathways of the module from airborne matter. The flexible dust cover has an elasticity that allows it to be temporarily deformed from its original shape to a stretched state by application of a stretching force to enable the module to be inserted into a central opening formed in the cover. The force is then removed, causing the cover to attempt to return to its original, non-stretched shape. When this happens, interior surfaces of the cover form a snug fit about exterior surfaces of the module. This snug fit fills in air gaps in the module that would otherwise be exposed to the environment.