A　novel　joint,　inspired　by　ancient　mortise-and-tenon　joints　in　timber　structures,　was　proposed　for　pultruded　FRP　beams　and　concrete-filled　FRP　columns.　FRP　structures　are　widely　known　to　lack　appropriate　joint　solutions.　In　this　regard,　the　proposed　joint　effectively　provides　a　feasible　solution　for　FRP　frame　structures.　In　this　work,　the　conceptual　development　of　this　joint　was　first　addressed.　Then,　the　construction　schemes　were　presented　in　detail,　and　a　total　of　four　full-scale　joints　were　tested.　To　assess　the　structural　behavior　of　the　proposed　joint,　experiments　including　four　specimens　were　conducted　under　symmetric　and　anti-symmetric　load,　i.e.　the　loading　conditions　in　sway　and　non-sway　frames.　The　typical　failure　modes　were　identified,　including　pull-out　or　tensile　fracture　of　the　tensile　flanges　and　end　crushing　of　the　compressive　flange.　Additionally,　an　analytical　study　is　carried　out　to　develop　the　design　method　for　this　joint.　The　predicted　moment　capacity　is　found　to　have　an　excellent　accuracy　as　compared　to　the　experimental　results.　Moreover,　the　proposed　joint　can　be　classified　as　the　rigid　and　full-strength　joint　based　on　the　classifications　prescribed　by　the　European　design　code.　It　is　noted　that　the　proposed　joint　is　completely　composed　of　FRP　composites　and　concrete　(i.e.,　a　steel-free　joint).　Thus,　the　joint　is　expected　to　exhibit　excellent　corrosion　resistance,　which　is　of　particular　interest　for　marine　structures　on/near　oceans.