This study aimed to evaluate the effects of fiberglass posts on fracture behavior in endodontically treated teeth (ETT) restored with composite veneers. Adult patients who had endodontically treated anterior teeth restored with composite veneers, with or without fiberglass posts, were divided into the case (with fractured teeth) and control (without fractured teeth) groups. All fracture patterns were sorted by a 6-point scoring system: 0, no fracture; 1, veneer buccal fracture; 2, incisal edge fracture; 3, coronal middle-third fracture; 4, coronal cervical fracture; 5, coronal and root fracture; and 6, root fracture. The odds ratio was calculated concerning the outcome (fracture) and exposed factor (post presence). Fracture patterns were analyzed by the Mann-Whitney and Fisher exact tests, with a significance level of 95%. Of the 89 ETT restored with composite veneers (31 with posts; 58 without posts), 30 were fractured. The odds ratio revealed a reduction in fracture risk to 34% compared with ETT without posts. Teeth without posts fractured more frequently, showing more complex fracture patterns. In conclusion, fiberglass posts decreased the risk of fractures in ETT restored with composite veneers.