Background Hypertension is an important risk factor for cardiovascular diseases and cognitive function. Blood pressure (BP) variability has been associated with cognitive dysfunction, but data are sparse regarding the relationship between BP variability and cognitive function in geriatric patients with well-controlled BP. Aim The aim of this study was to demonstrate the relationship between blood pressure variability and cognitive functions in geriatric hypertensive patients with well-controlled BP. Method We analyzed 435 hypertensive patients (167 male, 74.9 +/- 8.3; 268 female, 76.1 +/- 8.6) treated at least with one antihypertensive drug. All patients underwent ambulatory BP monitoring and the standardized mini mental test (sMMT). Results We divided the weighted standard deviation (SD) of systolic BP (SBP) as a measure of BP variability into quartiles. The top quartile group (>= 18.5 mmHg) had a significantly lower total sMMT score (23.3 +/- 3.2, p < 0.001). According to the results of multivariate logistic regression analysis for sMMT, the SD of 24-h SBP was related to sMMT (p = 0.007, 95% confidence interval - 0.301 [- 0.370 to - 0.049]). Discussion Although there are some inconsistencies among the studies investigating the relationship between blood pressure variability and cognitive functions in elderly patients, we demonstrated the relationship between increased 24-h blood pressure variability and cognitive functions assessed with sMMT in geriatric population with well-controlled BP. Conclusion The increased blood pressure variability was associated with poorer cognitive functions in geriatric hypertensive patients with well-controlled blood pressure.