Thin ply composites are quickly gaining interests in the composite industry not only because of the larger design space that they offer but also because of positive size effects that have been shown to affect their performance in various loading conditions [1]. In this work, carbon-epoxy composites of different ply thicknesses (30g/m2, 100g/m2 and 300g/m2 fiber areal weight) were produced from the same batch of Toray M40JB fiber and NorthTPT TP80ep matrix to study the influence of ply thickness on the ultimate strength and onset of damage of lamina and quasi isotropic laminates. Characterization tests on unidirectional lamina showed only limited influence of the ply thickness on the elastic and ultimate strength properties except for longitudinal compression in which the thinner ply specimens showed some advantage because of a more uniform microstructure. Uniaxial tension, open-hole compression and open-hole tensile fatigue tests on quasi isotropic [45°/90°/-45°/0°]ns laminates showed however very significant improvements of on-set of damage, and in some cases ultimate strength, when decreasing the ply thickness..These performance improvements could be related to a major change in the damage progression and failure modes of the laminates caused by a systematic delay or near suppression of transverse cracking and delamination growth in thin-ply composites. Detailed meso-scale finite element models of quasi isotropic unnotched tensile tests were developed and demonstrated that the increased stability of transverse intralaminar cracks was the main cause of the improved onset of damage of thin ply composites.