The COVID-19 pandemic has had lasting impacts on people's interpersonal relationship and mental health. Using four-wave data in China ( = 222, 54.50% female, = 31.53, = 8.17), the current study examined whether prepandemic relationship satisfaction was related to postpandemic COVID-19 anxiety through midpandemic perceived social support and/or gratitude. The results showed that people's COVID-19 anxiety decreased from the peak to the trough stage of the pandemic; perceived social support increased markedly from prepandemic to the peak and remained stable subsequently, while relationship satisfaction remained unchanged throughout. Further, it was midpandemic perceived social support, not gratitude, that mediated the association between prepandemic relationship satisfaction and postpandemic COVID-19 anxiety, indicating that perceived social support played a crucial role in this process. Finally, it is suggested that perceived social support should be distinguished from gratitude as two different components of social interactions.