The pistachio bark beetle, Chaetoptelius vestitus (Muls & Rey) (Coleoptera, Curculionidae, Scolytinae) is a serious pest of pistachio trees in Tunisia. Despite its important damage, its seasonal life cycle is still unclear. In this study, we investigated the seasonal life cycle and distribution of C. vestitus between November 2013 and October 2016 in the center and south of Tunisia. We recorded the direct damage caused by beetles on pistachio branches and buds. The highest density of C. vestitus attack was detected in Elguettar 2 site (Gafsa governorate). The insect overwinters both in adults and larval stage on pistachio trees. The adults emerge to attack new suitable trees at mid-May. Reproduction started in autumn: Also, females searched suitable hosts to attack. Copulation took place either on the bark in the initial phase of egg tunnel construction or inside the tunnel system. Mean fecundity was 50.95 (+/- 9.68 SD) eggs/female. The colonization process occurred in two phases. During the first phase, feeding galleries were drilled through, the buds. In the second phase, reproduction galleries were constructed in the thick branches of the tree. The results obtained in this work are considered essential for developing optimal control of the pest. Information on the seasonal life cycle allows to anticipate the time when plant damage may take place and to design the proper management of the pest.