Display omitted •The fatigue strength of AM Ti6A4V was improved by post-processing (surface peening)•Submerged laser peening (SLP), cavitation peening and shot peening were compared.•At SLP, laser ablation (LA) and laser cavitation (LC) were used.•At SLP, LA reduced surface roughness and LC introduced compressive residual stress.•Fatigue life improvements were estimated from surface roughness and residual stress. This study demonstrates the improvement in the fatigue strength of additive manufacturing (AM) metals such as laser-based powder bed fusion of metals by post-processing. Titanium alloy samples manufactured by powder bed fused (PBF) Ti6Al4V produced through laser sintering (LS), treated by submerged laser peening (SLP), cavitation peening (CP), and shot peening accelerated via a water jet (SPwj), were subjected to torsional fatigue testing and compared with the as-built specimen. At SLP, the samples were treated by laser ablation (LA) and laser cavitation (LC) which was developed following LA. A cavitating jet was used for CP. For comparison, conventional post-processing using SPwj was also performed. To characterize the microstructural modification caused by the three post-processing methods, the cross-section of the treated surface was observed by electron backscatter diffraction. The fatigue strengths at 107 cycles were found to be 217, 361, 313, and 285 MPa for the as-built, SLP, CP, and SPwj specimens, respectively. The primary factors contributing to fatigue strength improvement by post-processing were surface smoothing and the introduction of compressive residual stress. The experimental observations were used to derive correlation formulas to estimate the fatigue life improvement due to post-processing as the function of the surface roughness and surface residual stress.