This cross-sectional study investigated the relationship between self-reported chewing status and glycemic control in 32,137 Japanese adults who participated in health checkups. Chewing status was evaluated using a self-reported questionnaire. We defined poor glycemic control as a hemoglobin A1c (HbA1c) level ≥6.5% or the use of medication to control diabetes; 1,891 (5.9%) respondents met these criteria. After adjusting for gender, age, smoking status, exercise habits, body mass index, and eating speed, poor glycemic control was found to be positively associated with male gender (odds ratio [OR], 2.142; 95% confidence interval [CI], 1.903 to 2.411; p < 0.001), older age (OR, 1.093; 95% CI, 1.087 to 1.099; p < 0.001), higher body mass index (OR, 1.234; 95% CI, 1.219 to 1.249; p < 0.001), current smoker status (OR, 1.378; 95% CI, 1.223 to 1.552; p < 0.001), and ability to chew well (OR, 0.795; 95% CI, 0.699 to 0.904; p < 0.001). Furthermore, a negative association was found between the ability to chew well and poor glycemic control in those ≥40 years of age, but not in those between 20 and 39 years of age. In conclusion, self-reported ability to chew well was associated with poor glycemic control in Japanese adults aged ≥40 years.