© 2017 National Kidney Foundation, Inc. Background: Treating to a lower blood pressure (BP) may increase acute kidney injury (AKI) events. Study Design: Data for AKI resulting in or during hospitalization or emergency department visits were collected as part of the serious adverse events reporting process of the Systolic Blood Pressure Intervention Trial (SPRINT). Setting & Participants: 9,361 participants 50 years or older with 1 or more risk factors for cardiovascular disease. Interventions: Participants were randomly assigned to a systolic BP target of <120 (intensive arm) or <140 mm Hg (standard arm). Outcomes & Measurements: Primary outcome was the number of adjudicated AKI events. Secondary outcomes included severity of AKI and degree of recovery of kidney function after an AKI event. Baseline creatinine concentration was defined as the most recent SPRINT outpatient creatinine value before the date of the AKI event. Results: There were 179 participants with AKI events in the intensive arm and 109 in the standard arm (3.8% vs 2.3%; HR, 1.64; 95% CI, 1.30-2.10; P < 0.001). Of 288 participants with an AKI event, 248 (86.1%) had a single AKI event during the trial. Based on modified KDIGO (Kidney Disease: Improving Global Outcomes) criteria for severity of AKI, the number of AKI events in the intensive versus standard arm by KDIGO stage was 128 (58.5%) versus 81 (62.8%) for AKI stage 1, 42 (19.2%) versus 18 (14.0%) for AKI stage 2, and 42 (19.2%) versus 25 (19.4%) for AKI stage 3 (P = 0.5). For participants with sufficient data, complete or partial resolution of AKI was seen for 169 (90.4%) and 9 (4.8%) of 187 AKI events in the intensive arm and 86 (86.9%) and 4 (4.0%) of 99 AKI events in the standard arm, respectively. Limitations: Trial results are not generalizable to patients with diabetes mellitus or without risk factors for cardiovascular disease. Conclusions: More intensive BP lowering resulted in more frequent episodes of AKI. Most cases were mild and most participants had complete recovery of kidney function. Trial Registration: Registered at ClinicalTrials.gov with study number NCT01206062.