This study aimed to understand how the COVID-19 pandemic alters day-to-day relational experiences and how daily relational experiences shape outlook on the pandemic. Data were collected from university students in the U.S. using smartphone-based experience sampling and nightly diary surveys over a 10-day period beginning in April 2020. To address the first objective, we examined how pandemic-related anxiety and depressive symptoms manifested in three aspects of daily relational life: (a) perceptions of loneliness, (b) relational difficulty, and (c) communication quality. To address the second objective, we investigated how daily relational experiences were linked to their end-of-day outlook of the pandemic in terms of pessimism versus optimism regarding COVID-19 and general sense of hope. Over the 10-day study period, COVID-19-related anxiety was found to be uniquely associated with greater loneliness, desire for interaction when alone, interpersonal conflict, and distraction during communication episodes. In addition, results showed that relational experiences throughout the day, including loneliness, challenges maintaining relationships, and communication quality, were linked to end-of-day COVID-19 optimism and state hope. Overall, this study identifies potential ways in which young adults’ relational lives were altered during the first wave of the COVID-19 pandemic in the U.S. Results also suggest how relational experiences factor into daily social constructions of the pandemic.