Abstract: A mast support system for use with a container (e.g., a Connex container) to hold a light fixture, security camera and other accessories that may be desirable to mount above or from the roof of the container, generally comprising a support structure for purposes of supporting the accessories, and means to affix the support structure to the container. Embodiments of the mast support system disclosed include one or more posts removably attached to a base, which is engaged with the corner of a container. Attached to the posts are accessory support systems, extending therefrom for positioning and angling the accessories.