Objective: The purpose of the current study was to evaluate the marginal accuracy of minimal and no-preparation of two different machinable ceramic laminate veneers. Materials and methods: Twenty-eight extracted caries- and restoration-free human maxillary central incisors were used. The teeth were embedded in autopoly-merizing epoxy resin 2 mm apical to cement-enamel junction. The teeth were divided into 2 main groups (A& B) of 14 specimens, each main group is divided into 2 subgroups (A1, A2, N=7 & B1, B2, N=7). The labial surfaces of group (A) were prepared with 0.3 mm reduction to receive porcelain veneers.  The veneers were fabricated by either CAD-CAM block materials of polymer infiltrated (Vita enamic) and a lithium disilicate glass ceramic (IPS e.max CAD). The veneers were acid etched using hydrofluoric acid, silanated, and cemented on their corresponding prepared and no-prepared teeth. Results: Machinable ceramic veneers (Vita enamic) demonstrated significantly lower marginal gaps and micro-leakage than that of  [IPS e-max CAD] ceramic veneers and no statistical significant difference regarding internal adaptation within  the two machinable materials. Conclusions: The following conclusions in this in-Vitro study could be obtained; Polymer infiltrated machinable (Vita enamic) veneers produced higher marginal accuracy compared to glass-ceramic machinable (IPS e.max CAD) veneers. Minimally invasive preparation design enhance the marginal accuracy compared to no-preparation design.