INTRODUCTION: There is a challenge on the medical efficacy of intravesical Bacillus Calmette-Guérin (BCG) therapy and the power of the immune system boosting, which can be influenced by the age of the non-muscle-invasive bladder cancer (NMIBC) patients. This meta-analysis evaluates the efficacy of BCG therapy among aged (>70) and younger patients with non-muscle-invasive bladder cancer (NMIBC). METHODS: The central database of PubMed, Scopus, and Web of Science were queried until August 4, 2021, by using `BCG,` `Bladder Cancer,` `AGE,` and `efficacy` keywords. After excluding duplicated results, titles and abstracts were evaluated by two independent reviewers. The exclusion criteria included non-English studies, conference abstracts, reviews, editorials, letters, and comments. Three main outcomes, disease-free survival (DFS), progression-free survival (PFS), and cancer-specific survival (CSS), were considered. The statistical analysis was performed using STATA (version 14; Stata Corp, College Station, Texas, USA). RESULTS: From 1115 found documents, the 24 research articles were recruited in the systematic review, and 10 were the candidate for meta-analysis. The overall estimate of H.R. revealed that BCG therapy in those over age 70 is significantly associated with an improved risk of progression and cancer-specific death in studied patients. However, this association was not statistically significant for DFS (1.04 (95% CI: 0.85,1.26)). CONCLUSION: The BCG maintenance therapy improved CSS and PFS oncological outcomes in elderly patients with NMIBC. BCG therapy did not significantly change the DSF.