Overuse and misuse of antibiotics have led to the emergence of antibiotic-resistant bacteria and pose a significant threat due to adverse drug reactions, increased healthcare costs, and poor patient outcomes. Antibiotic stewardship programs, including antibiotic de-escalation, aim to optimize antibiotic use and to reduce the development of antibiotic resistance. This systematic review and meta-analysis aim to fill the gap by analyzing the current literature on the implications of antibiotic de-escalation in patients on antibiotic use, duration of hospital stay, mortality, and cost; to update clinical practice recommendations for the proper use of antibiotics; and to offer insightful information about the efficacy of antibiotic de-escalation. Based on the PRISMA 2020 recommendations, a comprehensive literature search was conducted using electronic databases and reference lists of identified studies. Eligible studies were published in English, conducted in humans, and evaluated the impact of antibiotic de-escalation on antibiotic consumption, length of hospitalization, mortality, or cost in hospitalized adult patients. Data were extracted using a standardized form, and the quality of included studies was assessed using the Newcastle–Ottawa Scale. The data from 25 studies were pooled and analyzed using the Revman-5 software, and statistical heterogeneity was evaluated using a chi-square test and I2 statistics. Among the total studies, seven studies were conducted in pediatric patients and the remaining studies were conducted in adults. The studies showed a wide range of de-escalation rates, with most studies reporting a rate above 50%. In some studies, de-escalation was associated with a decrease in antimicrobial utilization and mean length of stay, but the impact on overall cost was mixed. Our pooled analysis for mortality reported that a significant difference was observed between the de-escalation group and the non-de-escalation group in a random effect model (RR = 0.67, 95% CI 0.52–0.86, p = 0.001). The results suggest that de-escalation therapy can be applied in different healthcare settings and patient populations. However, the de-escalation rate varied depending on the study population and definition of de-escalation. Despite this variation, the results of this systematic review support the importance of de-escalation as a strategy to optimize antibiotic therapy and to reduce the development of subsequent antibiotic resistance. Further studies are needed to evaluate the impact of de-escalation on patient outcomes and to standardize the definition of de-escalation to allow for better comparison of studies.