The aim of this study was to compare radiographic and clinical status and peri-implant sulcular fluid (PISF) prostaglandin E2 (PGE2) levels among patients with and without peri-implant disease. Patients with peri-implant mucositis (PiM) (Group 1) and peri-implantitis (Group 2) and individuals without peri-implant disease (Group 3) were included. Demographic information was collected, and peri-implant modified plaque and bleeding indices (mPI and mBI), probing depth (PD), and crestal bone loss (CBL) were recorded. PISF samples were collected and PGE2 levels measured. Statistical significance was set at P < .01. A total of 22 patients with PiM, 22 with peri-implantitis, and 23 without peri-implant disease (controls) were included. Scores of mPI (P < .01), mBI (P < .01), and PD (P < .01) were higher in patients with PiM and peri-implantitis than the controls. The volumes of collected PISF were significantly higher in patients with peri-implantitis (P < .01) compared to patients with PiM and the controls. The PISF volume was significantly higher in PiM patients (P < .01) than in the controls. There was a significant correlation between peri-implant PD and PISF PGE2 levels in patients with peri-implantitis (P < .001). Raised PISF PGE2 levels indicate poor peri-implant health; therefore, PGE2 is a potential biomarker for the assessment of peri-implant health status.