Some peritoneal dialysis (PD)‐related peritonitis cases are thought to be caused by the pathogens in the oral cavity; however, the relationship between peritonitis and oral hygiene habits is unclear. In this study, we retrospectively examined the relationship between oral hygiene habits and peritonitis in patients who agreed to a questionnaire survey. Of the 75 patients, 37 patients developed PD‐related peritonitis during the observation period. Peritonitis‐free survival was significantly higher in patients who spent more time on oral hygiene daily and in patients who replaced their toothbrush more frequently (P < 0.05). According to multivariable analysis, increased daily oral hygiene duration and more frequent toothbrush replacement were associated with a significantly (P < 0.01) lower risk for peritonitis (hazard ratio [HR] 0.37 [95% CI, 0.18–0.77] and HR 0.35 [95% CI, 0.17–0.70], respectively). In conclusion, PD patients with superior oral hygiene habits showed a lower risk for PD‐related peritonitis.