In the absence of a definitive therapy during this ongoing unprecedented crisis, coronavirus disease-2019 (COVID-19) pandemic, convalescent plasma transfusion (CPT) has shown some promising results. This review summarizes the existing evidence of the efficacy of CPT in COVID-19 patients based upon scientific publications to date. We have included only the randomized controlled trials (RCTs) through an extensive screening of electronic databases up to July 31, 2021. In 19 RCTs, with a total of 16,476 COVID-19 patients we found low-quality evidence of significant reduction in mortality (odds ratio (OR) = 0.80; 95% confidence interval (CI): 0.66–0.96, I² = 40%), better clinical outcome when applied <7 days (OR = 2.13, 95% CI 1.28–3.53, I² = 0%), and improved viral clearance (OR = 2.6, 95% CI: 1.3–5.45, I² = 74%). Meta-regression analysis found that as a covariate, intubation on admission (p = 0.007) had a significant impact. However, there was any significant reduction neither in duration for clinical improvement (MD = −0.79, 95% CI: −2.76–1.18, I² = 98%), nor in total period of hospital stay (MD = 0.02, 95% CI: −0.75–0.78, I² = 81%). Early application of CPT is still relevant in reducing morbidity and mortality in critically ill patients and is too early to write it off as a potential therapeutic modality for COVID-19 patients.