Background: Young adults in Hong Kong, especially those who live in crowded living spaces, are at risk of anxiety during the pandemic. The social contact patterns of young adults have been greatly affected by the implementation of social distancing measures which can possibly affect their anxiety levels. This study aimed to investigate the effect of social contact patterns on buffering the negative effect of crowded living environment on anxiety level as well as the relationship between social contact pattern and anxiety level of young adults in Hong Kong. Methods: Participants were asked to complete the online questionnaire, including demographic information, self-developed social network survey, living environment, items related to the susceptibility and severity of COVID-19 and DASS21 (anxiety sub-scale). Results: To this end, 427 participants were included in the study. A significant association between crowded living environment and anxiety level was showed (P=0.009), as well as the positive effects of non-physical contact (β=-0.418, p<0.001), physical contact (β=-0.257, p=0.015) and closed contact (β=-0.576, p<0.001) on the anxiety level of young adults. A significant buffering effect of social contact patterns on the association between moderate (β=-0.120, p=0.005), highly crowded living environment (β=-0.307, p<0.001), and anxiety level is observed. Conclusions: Social contact patterns have a positive impact on reducing the anxiety level of young adults in Hong Kong and it can act as a buffer for people living in highly dense environments who have a higher anxiety level.