A locking production seal assembly is shown for sealing a well tubing string within the bore of a surrounding well conduit which has been provided with an internal recess. The seal assembly includes a sliding mandrel which is made up in the well tubing string and an outer sleeve which is carried about the mandrel. The outer sleeve has an external seal for sealing with the interior of the surrounding conduit and an internal seal for sealing with the sliding mandrel. A setting sleeve carried between the mandrel and outer sleeve carries a set of setting dogs for engaging the surrounding conduit and a set of locking dogs for locking the setting sleeve to the surrounding sleeve once the assembly is set. The load carrying setting dogs are separated from the mandrel exterior by the setting sleeve to prevent damage to the mandrel exterior.