Background: The epidemiology of acute renal dysfunction after stroke is routinely overlooked following stroke events. Our aim in this meta-analysis is to report the prevalence of acute kidney injury (AKI) following acute stroke and its impact on mortality. Methods: A systematic literature search was performed on PubMed, EMBASE and Google Scholar for observational studies examining the prevalence and mortality risk of stroke patients with AKI as a complication. The pooled prevalence rates and odds ratios for mortality risk were calculated using subgroup analyses between the stroke subtypes: acute ischemic stroke (AIS) and intracerebral hemorrhage (ICH). Results: A total of 12 studies (4,532,181 AIS and 615,636 ICH) were included. The pooled prevalence rate of AKI after all stroke types was 11.6% (95% CI 10.6–12.7). Subgroup analyses revealed that the pooled prevalence rate of AKI after AIS was greater but not statistically significantly different than ICH (19.0%; 95% CI 8.2–29.7 vs. 12.9%; 95% CI 10.3–15.5, p = 0.5). AKI was found to be a significant risk factor of mortality in AIS (adjusted OR [aOR] 2.23; 95% CI 1.28–3.89; I2 = 98.8%), whereas this relationship did not reach statistical significance in ICH (aOR 1.20; 95% CI 0.68–2.12; I2 = 74.2%). Conclusions: This meta-analysis provides evidence that AKI is a common complication following both AIS and ICH and it is associated with increased mortality following AIS but not ICH. This highlights the need for early assessment of renal function in the acute phase of AIS, in particular, and avoidance of factors than may induce AKI in vulnerable patients.