Background Frailty and cognitive impairment are common in the elderly, with various shared risk factors like hypertension. Frailty is a marker for future cognitive function. Moreover, whether intensive blood pressure interacted with frailty and cognitive impairment is unknown. Methods and Results We performed a post hoc analysis of data from SPRINT (Systolic Blood Pressure Intervention Trial). The relationship between frailty and a composite of probable dementia (PD) and mild cognitive impairment (MCI) was analyzed. Also, we evaluated the interaction of intensive blood pressure lowering in the relationship between frailty and cognitive impairment. A total of 8537 patients were included in our study, and 35.1% were women. The mean age of these participants was 67.9±9.3 years. According to the baseline frailty index, 1670, 4637, and 2230 patients were in fit, less fit, and frail statuses, respectively. During a mean follow-up of 4.61 years, 871 cases of PD or MCI occurred. Compared with those in fit status, those with less fit (hazard ratio [HR], 2.14 [95% CI, 1.65-2.77]) and frailty (HR, 4.28 [95% CI, 3.26-5.61]) status had a higher incidence of a composite of PD and MCI. Blood pressure control strategy interacted with the correlation between frailty and cognitive impairment. Intensive blood pressure control (HR, 2.4 [95% CI, 2.0-2.8]) accelerated the relationship between frailty and incidence of PD and MCI compared with the standard treatment group (HR, 1.8 [95% CI, 1.5-2.1]; P for interaction=0.009). Conclusions This study found that the baseline frailty status was a possible marker for the incidence of a composite of PD and MCI. Intensive blood pressure control may strengthen this correlation. Registration URL: https://clinicaltrials.gov/; Unique identifier: NCT01206062.