The role of the direct renin inhibitor aliskiren in hypertension is not fully established and use of aliskiren in diabetic patients is especially controversial. A systematic review investigating both short-term diastolic and systolic blood pressure (DBP and SBP) reduction and long-term cardiovascular outcomes has not been conducted. Therefore, we aimed to fill this gap by investigating BP reduction, major cardiovascular outcomes, and mortality of aliskiren compared to other antihypertensive therapy. We searched PubMed and Embase databases for relevant randomized controlled trials (RCTs). Using a random-effects model, weighted mean difference (WMD) and relative risk (WRR) with 95% confidence interval (CI) were used to measure the effect of aliskiren therapy in the management of hypertension and major cardiovascular outcomes. Thirty seven RCTs with a total of 35,916 patients were included. Aliskiren induced slightly greater DBP and SBP reductions than other antihypertensive agents (WMD -0.77 mmHg, 95% CI [-2.01;0.46 mmHg] and WMD -1.14 mmHg, 95% CI [-2.78;0.50 mmHg], respectively). Aliskiren did not reduce total mortality or cardiovascular death. In patients with diabetes, aliskiren add-on therapy may have the potential to increase total mortality and cardiovascular death (WRR 1.06, 95% CI [0.88;1.28] and WRR 1.09, 95% CI [0.94;1.24], respectively). Despite superior BP-reducing effect, aliskiren is not recommended as first-line treatment in hypertensive patients as it does not reduce mortality and major cardiovascular outcomes. Dual renin-angiotensin-aldosterone system inhibition with aliskiren should be avoided in diabetic patients, while the use of aliskiren monotherapy remains to be investigated.