In many nations, overcrowding in emergency departments (EDs) is a serious public health issue that threatens the proper operation of health systems. Understanding the connection between overcrowding and delays in ED treatment provides decision-makers with valuable insights into the problem and supports the implementation of timely solutions. This meta-analysis adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses standards and focuses on evaluating the impact of overcrowding in emergency departments (EDs) on patient care outcomes. Specifically, it synthesizes existing data to identify both the causes of ED overcrowding and its effects on patient outcomes. This review screened 11 articles published between 2010 and 2024, including a total of 3,084,344 patients. Among them, 14.7% were admitted to hospitals, with 49% male and 51% female. The average age was 35.9 years, ranging from 3.9 to 58 years, with a median age of 37.3 years. The minimum waiting time before the first examination was 30 min, with a maximum of 360 min and a mean of 234.0 ± 21.7 min. The total length of stay (LOS) in the ED ranged from 123.5 to 540.0 min, with a mean of 245.8 ± 95.9 min. Most patients were discharged home (67.6%), while 10.9% returned to the ED due to unresolved or worsening conditions. Additionally, 2.31% of patients died, 1.88% eloped, 3.08% left without being seen (LWBS), and 1.27% required ICU admission. This meta-analysis highlights the pervasive impact of ED overcrowding on patient outcomes, healthcare worker well-being, and care quality. Overcrowding prolongs waiting times and LOS, disproportionately affects low-acuity cases, and compromises critical care for high-severity patients. Adverse events, such as LWBS, revisits, and incomplete assessments, are consistently linked to overcrowded conditions. Healthcare workers experience significant stress and burnout, which contributes to medical errors and reduced service efficiency.