Objectives <p>This retrospective cohort study evaluated the association between implant adjacency and survival of endodontically treated teeth (ETT) and assessed factors associated with tooth loss due to vertical root fracture (VRF).</p> Materials and methods <p>Patient charts were reviewed to identify teeth adjacent and nonadjacent to implants. The primary outcome was cumulative survival of ETT by tooth location and implant adjacency. VRF was the secondary outcome. Kaplan–Meier analysis with log-rank tests compared survival, and multivariable logistic regression with generalized estimating equations accounted for clustering.</p> Results <p>A total of 787 patients with 2,048 adjacent and 15,637 nonadjacent teeth were included (mean follow-up: 57.1 months). Among 1,119 ETT, survival was highest in nonadjacent anterior teeth (126.5 months), followed by nonadjacent posterior (84.8 months), adjacent anterior (55.6 months), and adjacent posterior teeth (44.4 months) (<i>p</i> &lt; 0.001). Sixty-three ETT (5.63%) were lost due to VRF. ETT adjacent to implants had significantly higher odds of VRF (aOR = 8.90; 95% CI, 4.03–19.64; <i>p</i> &lt; 0.001), and post placement was independently associated with increased risk.</p> Conclusions <p>Implant adjacency and posterior location were associated with reduced survival of ETT. Implant adjacency and post placement were independently associated with an increased risk of tooth loss due to VRF.</p> Clinical relevance <p>ETT adjacent to dental implants may have reduced survival, particularly in posterior regions. Clinicians should be aware of the increased risk of VRF in these teeth, especially when post placement is present. Careful occlusal management and regular follow-up may help mitigate the risk of tooth loss.</p>