The height of the COVID-19 pandemic was an exceptionally stressful time for families that offered a unique opportunity to understand how stressful experiences occurring outside the relationship shape behavior occurring inside the relationship. Given the social distancing requirements of the pandemic, however, most research addressing this issue has relied on self-reports of behavior, which are susceptible to bias. In the summer of 2020, we asked a sample of married individuals living in the United States, Canada, Ireland, and the United Kingdom to complete online questionnaires assessing neuroticism and attachment insecurity, their levels of chronic stress, and their levels of acute stress due to the COVID-19 pandemic. We then asked participants to submit a 10-min video of themselves and their spouse attempting to solve an important marital problem that they recorded on their smartphone or other device and uploaded to a secure server. Coders were able to reliably code the behavior of both partners using an established coding system, and the distribution of codes was similar to prior research. Consistent with predictions, participants’ COVID-19 stress interacted with their neuroticism and attachment avoidance to predict their levels of oppositional behavior, controlling for their levels of chronic stress and their partner’s behavior; neuroticism and attachment avoidance were associated with behaving in a more oppositional manner among participants who reported high but not low COVID-19 stress. Attachment anxiety trended toward predicting more oppositional behavior regardless of stress. These results shed light on how stress affects behavior and introduce a novel way to observe family behavior remotely.