Purpose: The primary objective of this study was to assess the accuracy of periapical radiographs in determining the peri-implant marginal bone level. The accuracy of the linear measurements on radiographs was considered as the absolute difference between the true, intraoperative or surgical marginal bone level measurements (direct bone measurements during surgical procedures) and the radiographic measured distances. The secondary aims were to identify the variables influencing the radiographic evaluation (arch: mandible/maxilla; implant location: anterior/posterior; timing of implant placement: "early delayed" and "prolonged delayed"). The influence of vestibular and palatal/lingual crestal bone levels was also investigated. Materials and Methods: STROBE guidelines were followed. As soon as the implant was inserted, the marginal bone levels were recorded using a straight periodontal probe (intraoperative or surgical measurements). At the same time, periapical radiographs were taken. To standardize the radiographic images, periapical radiographs were acquired using the long-cone parallel technique and film holding system. All radiographs were analyzed by two examiners blinded to the surgical measurements. Intraclass correlation coefficient (ICC) was employed to assess the intraobserver and interobserver variability. The descriptive statistics, t test, and multivariate statistics were used; the threshold for statistical significance was P ≤ .05. Results: Two hundred sixty-eight implants were inserted in 142 patients. The interobserver agreement was 0.980; the intraobserver variability was 0.990 and 0.993. The mean difference between the radiographic and surgical measurements was 0.45 mm (range: 0 to 8 mm; SD: 1.76). Comparing the radiographic and surgical measurements, a statistically significant difference (P = .000) was detected. None of the variables considered (arch, implant location, and timing of implant placement) significantly influenced the accuracy. Neither the vestibular alveolar edge (P = .908) nor the lingual/palatal (P = .485) significantly influenced the accuracy. Conclusion: The periapical radiograph statistically significantly overestimates the level of periimplant marginal bone compared with surgical measurements. The arch, implant location, timing of implant placement, and level of vestibular or lingual/palatal alveolar edge do not influence deviation between the intraoperative peri-implant marginal bone level measurements and the radiographically determined marginal bone levels. Keywords: alveolar bone loss, computer-assisted, dental implant, dental radiography, radiographic image interpretation