A lightbar assembly connector for use in a modular lightbar system to connect two or more lightbar assemblies together and having a design and configuration that enables the lightbar assembly connector and lightbar assemblies to be connected by moving the lightbar assembly connector in a direction generally transverse to the longitudinal axis of the lightbar assembly (or by moving the lightbar assembly in a direction generally transverse to the major surface of the lightbar assembly connector). It is thus possible to assemble a modular lightbar system comprised of a plurality of lightbar assemblies and lightbar assembly connectors, any of which are easily removable, replaceable, or serviceable without having to remove or move lightbar assemblies that do not need to be replaced or serviced.