The COVID-19 pandemic has presented significant challenges to mental health worldwide, exacerbating mental health symptoms across various populations. This meta-analysis aims to evaluate the relationship between social support and mental health symptoms, specifically depression, general anxiety, and stress, during the pandemic. We conducted a comprehensive literature search that identified 210 studies involving a total of 216,104 participants. Data were analyzed using robust variance estimation with random effects to assess correlations between social support and mental health symptoms, while also examining potential moderating factors such as age, gender, and sample types. Our analysis revealed a significant negative correlation between social support and overall mental health symptoms (r = -0.259; 95% CI: -0.29, -0.24; p < 0.01). Notably, high-risk populations exhibited a stronger association (r = -0.302) compared to students (r = -0.263) and the general population (r = -0.219). Furthermore, the correlation between social support and depression (r = -0.304) was significantly stronger than that for generalized anxiety (r = -0.238) and stress (r = -0.220), underscoring the critical role of family support during this period. These findings suggest that while social support positively influences mental health symptoms, its effectiveness may be more limited than anticipated. As the pandemic continues to impact mental well-being, there is an urgent need for targeted strategies to enhance the effectiveness of social support in addressing mental health challenges. This research highlights the importance of prioritizing social support mechanisms in public health responses to future crises.