Abstract: Due to the geometry complexity, stress concentration is normally observed at the weld toe. This study proposed a scheme of prestressed CFRP sheets for fatigue strengthening of circular hollow section (CHS) T-joints. Static axial tension loading was applied to the brace of five prestressed CFRP strengthened CHS T-joints and one reference specimen to compare hot spot stress distribution in the chord along the weld toe. Afterward, the specimens were subjected to tension-tension fatigue cycles. The fatigue failure mode was carefully recorded. Fatigue lives in three fatigue failure criteria were determined and compared, including the crack initiation fatigue life N₂, the through thickness fatigue life N₃, and the end of test fatigue life N₄. The scheme of prestressed CFRP sheets for the fatigue strengthening was proved feasible, since no CFRP fracture, debonding or slip were found during static and fatigue loading. Uneven compressive hot spot stress in the chord along the weld toe was introduced due to CFRP prestress, leading to change in distribution of the initial hot spot stress. The maximum hot spot stress was significantly reduced by up to 38%. The fatigue failure mode was changed due to introduction of prestress. The prestressed CFRP strengthened CHS T-joints exhibited a longer fatigue life than that of the unstrengthened joint regardless of fatigue failure criteria (N₂, N₃, or N₄), where the maximum extension in N₂ was 126%.