Objectives To conduct a systematic review to elucidate the frequency, recovery, and associated outcomes for poststroke aphasia over the long-term. Data Sources Using the Cochrane Stroke Strategy, we searched 10 databases, 13 journals, 3 conferences, and the gray literature. Study Selection Our a priori protocol criteria included unselected samples of adult stroke patients from randomized controlled trials or consecutive cohorts. Two independent reviewers rated abstracts and articles for exclusion or inclusion, resolving discrepancies by consensus. Data Extraction We documented aphasia frequencies by stroke type and setting, and computed odds ratios (ORs) with their 95% confidence intervals (CIs) for outcomes. Data Synthesis We retrieved 2168 citations, reviewed 248 articles, and accepted 50. Median frequencies for mixed stroke (ischemic and hemorrhagic) were 30% and 34% for acute and rehabilitation settings, respectively. Frequencies by stroke type were lowest for acute subarachnoid hemorrhage (9%) and highest for acute ischemic stroke (62%) when arrival to the hospital was ≤3 hours from stroke onset. Articles monitoring aphasia for 1 year demonstrated aphasia frequencies 2% to 12% lower than baseline. Negative outcomes associated with aphasia included greater odds of in-hospital death (OR=2.7; 95% CI, 2.4–3.1) and longer mean length of stay in days (mean=1.6; 95% CI, 1.0–2.3) in acute settings. Patients with aphasia had greater disability from 28 days (OR=1.5; 95% CI, 1.3–1.7) to 2 years (OR=1.7; 95% CI, 1.6–2.0) than those without aphasia. By 2 years, they used more rehabilitation services (OR=1.5; 95% CI, 1.3–1.6) and returned home less frequently (OR=1.4; 95% CI, 1.2–1.7). Conclusions Reported frequencies of poststroke aphasia range widely, depending on stroke type and setting. Because aphasia is associated with mortality, disability, and use of health services, we recommend long-term interdisciplinary vigilance in the management of aphasia.