A fence post assembly for mounting to a substructure with a single point of attachment. The post assembly has an outer sleeve surrounding a support member and an attachment rod extending through the support member. The post assembly is mounted to the substructure by securing one end of the attachment rod in the substructure and securing the support member between a compression plate and the substructure by tensioning the upper end of the attachment rod. Attachment points for securing additional fence components to the post are provided by inserting an adapter into a receiving channel defined along a longitudinal length of the support member.