BACKGROUND: Excessive use of smartphones and the Internet can lead to addiction and may increase the risk of developing mental disorders, particularly in the context of the COVID-19 outbreak. OBJECTIVE: This systematic review and meta-analysis synthesized the existing literature reporting the impact of smartphone and Internet addiction on mental health during the COVID-19 pandemic. METHODS: A systematic search was performed on two databases, PubMed and EMBASE, following the PRISMA guidelines to identify articles conducted from December 2019 when the COVID-19 pandemic began to emerge. Studies were selected based on pre-defined criteria and assessed for quality before inclusion in the meta-analysis. The main effect estimate gathered from eligible studies was the odds ratio, which was computed using the random-effects model. RESULTS: Our findings demonstrated significant associations between Internet addiction and depression (OR = 4.09, 95% CI [3.28, 5.09]), Internet addiction and anxiety (OR = 3.08, 95% CI [2.08, 4.57]), smartphone addiction and depression (OR = 3.82, 95% CI [3.31, 4.40]), and smartphone addiction and anxiety (OR = 4.81, 95% CI [3.81, 6.07]) during the COVID-19 pandemic. CONCLUSION: This meta-analysis underscores that Internet and smartphone addiction increases the likelihood of developing mental disorders in the context of the COVID-19 pandemic. During the outbreak of infectious diseases, it is imperative for nations to not only address economic and educational challenges but also prioritize the mental well-being of their citizens.