Background: Retrospecting the trust gaps and their dynamics during the pandemic is crucial for understanding the root causes of postpandemic challenges and offers valuable insights into preparing for future public health emergencies. The COVID-19 pandemic eroded people’s trust in strangers and acquaintances, while their trust in family members remained relatively stable. This resulted in 2 trust gaps, namely, the family members–strangers trust gap and the family members–acquaintances trust gap. Widening trust gaps impede social integration and undermine the effective management of public health crises. However, little is known about how digital media use shaped trust gaps during a pandemic. Objective: This study aims to investigate the relationships between digital media use, negative emotions, the family members–strangers trust gap, and the family members–acquaintances trust gap during the COVID-19 pandemic in China. We test the mediating role of negative emotions between digital media use and 2 trust gaps and compare the indirect effect of digital media use on 2 trust gaps through negative emotions. Methods: A cross-sectional web-based survey was conducted in China between January 31, 2020, and February 9, 2020. A total of 1568 adults participated in the survey. Questions related to digital media use, negative emotions, trust in family members, trust in acquaintances, and trust in strangers during the pandemic were asked. Regression analyses were performed to test the associations between the examined variables. We used a 95% bootstrap CI approach to estimate the mediation effects. Results: Digital media use was positively associated with negative emotions (B=0.17, SE 0.03; P<.001), which in turn were positively associated with the family members–strangers trust gap (B=0.15, SE 0.03; P<.001). Likewise, digital media use was positively associated with negative emotions (B=0.17, SE 0.03; P<.001), while negative emotions were positively associated with the family members–acquaintances trust gap (B=0.08, SE 0.03; P=.01). Moreover, the indirect effect of digital media use on the family members–strangers trust gap (B=0.03, SE 0.01; 95% CI 0.01-0.04) was stronger than that on the family members–acquaintances trust gap (B=0.01, SE 0.01; 95% CI 0.003-0.027). Conclusions: The results demonstrate that negative emotions resulting from the frequent use of digital media are a key factor that accounts for the widening trust gaps. Considering the increasing reliance on digital media, the findings indicate that the appropriate use of digital media can prevent the overamplification of negative emotions and curb the enlargement of trust gaps. This may help restore social trust and prepare for future public health crises in the postpandemic era.