Purpose: The objective of this study was to use patient-reported outcome to explore patient characteristics that influence the oral health-related quality of life of post-implant patients. Materials and Methods: The study design was a nested case-control study. The target population was patients who had undergone implant treatment at the Department of Oral Implantology, Osaka Dental University, with a superstructure fitted ≥ 3 months previously. The survey period was from April 2014 to the end of October 2016. Oral health-related quality of life was evaluated using the General Oral Health Assessment Index (GOHAI). The relationship between patient characteristics and oral health-related quality of life was investigated by binomial logistic regression analysis. The Japanese GOHAI norm for the 50s and 60s age groups was used as the dependent variable for comparison with this study population. Explanatory variables were age, sex, time of survey, implant site, type of superstructure, pre-implant number of molar occlusal support zones, pre-implant deficit status, and number of missing teeth. Results: Of the total of 1,967 subjects, data were missing for 176 subjects, the time of survey was 3 months since fitting of the superstructure for 1,021 subjects, and 123 subjects did not meet the inclusion criteria. Therefore, 647 subjects were finally analyzed. As a result of implant treatment, 64.5% of subjects exceeded the Japanese GOHAI norm for the same age group (52.2). From logistic regression analysis, patient characteristics that were extracted as influencing oral health-related quality of life were age 65 years (odds ratio: 1.8); women (odds ratio: 1.8); and 1 preimplant molar occlusal support zone (reference value of 4 zones) (odds ratio: 2.5). Conclusion: This study showed that implant treatment is an effective method for dental prosthetic treatment from the perspective of patient-reported outcome. In addition, patient characteristics that influence the oral health-related quality of life of post-implant patients were shown to be age 65 years, women, and one pre-implant molar occlusal support zone. This study may help to predict posttreatment oral health-related quality of life and determine treatment plans. Keywords: dental implant treatment, General Oral Health Assessment Index, GOHAI, logistic regression analysis, oral health-related quality of life, patient-reported outcome