The article presents the impact of welding non-conformities on microhardness of EN AW 5754 aluminium alloy welded joints made with the use of the TIG method. The results of microhardness tests of welded samples made with various process parameters. The impact of the welding non-conformities disclosed with the use of a tomographic method on the welded joint microhardness were analysed. The studies showed a strong link between the participation of welding non-conformities, welding process parameters and microhardness of welds.