This study evaluated the accuracy of implant placement with surgical-template guidance both in vitro and in vivo. Virtual surgical planning was performed based on the data from CBCT scans and an intraoral scanner. Surgical templates were designed according to the planned implants and manufactured with stereolithography. In vitro, 60 implants were placed in 15 resin models. In vivo, 74 implants were placed in 54 patients. The implants were scanned with CBCT postoperatively. Implant accuracy was evaluated by measuring the following parameters: central deviation at the apex and shoulder, horizontal deviation at the apex and shoulder, vertical deviation at the apex and shoulder, and angular deviation. There were statistically significant in vitro and in vivo deviations for all parameters, and the implant deviations in vivo were significantly greater than those in vitro. When using a mucosa-supported template, horizontal deviations at the apex were significantly greater than when a teeth-supported template was used. Within the limitation of the study design, inaccuracy existed in implant placement guided with a surgical template. More studies are needed to investigate the value of the procedure in future.