<p>The COVID-19 pandemic and the ensuing control measures such as lockdown and isolation have led to widespread global disruptions, disproportionately impacting socioeconomically disadvantaged populations already at elevated risk of adverse mental health outcomes. This review aimed to synthesize the pooled prevalence of mental health problems among socioeconomically disadvantaged groups during the pandemic. A systematic search of English, Chinese, and preprint databases was conducted through August 2024. The analysis incorporated 47 studies, encompassing a total of 318,206 participants. The pooled prevalence of depressive symptoms, anxiety symptoms, and stress symptoms was 31% (95%CI: 23%-41%), 22% (95% CI: 15%-31%), and 23% (95% CI: 8%-52%), respectively. However, substantial heterogeneity was observed across studies (<i>I</i>^<i>2</i> &gt; 99%), warranting cautious interpretation of the pooled estimates. Key factors associated with high prevalence included socioeconomic status, geographic location, the use of specific screening tools, the Oxford COVID-19 Stringency Index, and the Economic Support Index. These findings highlight the critical need for policymakers and healthcare providers to address the mental health needs of these vulnerable populations through targeted interventions and proactive preparation for future public health crises.</p>