This paper presents the findings ofan ilwestigative study on the effects of seam geometries on the mechanical properties of seamed geotextiles. In this study, wide width tensile strip, grab and CBR cone plunger mechanical tests were conducted on three types of non-wovens with similar unit weight. The seamed geotextile specimens were jointed together with different seam geometries, flat, lapped, capped, butterfly and J seams respectively. In order to reduce the influence of the stitch geometries and the frictional effect of sewing threads, either single or double rows of 401 type chain stitches, formed with a lightweight, smooth sewing thread were adopted in the tests. With respect to the tensile strip and grab test results, tensile pulling and frictional type of seam, capped and lapped seams with double rows of stitches have demonstrated that they were suitable for all types of geotextile, even needle punched, and their performance showed superiority over the other seam types depending on the tensile pulling of the flat, butterfly and J seams respectively. All seams withstood punching well, due to the beam effect. In conclusion, a tighter seam can produce a higher strength ratio. Tensile pulling and frictional types of seams, or lapped and capped, provide economical and effective joints. Double stitching rows can provide a better degree of security to the seam, guaranteeing service performance.