This study examined how peer assessment and self-assessment influence higher education students' use of three modes of regulation of learning (self-regulation, co-regulation, and socially shared regulation) in an online collaborative task during the COVID-19 epidemic. Twenty-one first-year undergraduate students were assigned to one of three assessment conditions: self-assessment, written peer assessment, or oral peer assessment. Interview data was coded into 709 meaningful segments using content analysis and a deductive coding matrix. Segments were then investigated both qualitatively and using Chi2 quantitative analyses to explore five research questions. Results suggest (a) significant emotional difficulty was associated with peer assessment, both written and oral; (b) although negative affect was associated with the online learning context, this was mitigated in part by the self-assessment condition; (c) self-regulatory processes were more prevalent in the self-assessment condition than in the synchronous (oral) peer-assessment condition; (d) peer assessment was not associated with higher levels of socially shared regulation than self-assessment; (e) socially shared regulatory processes were not more prevalent when peer assessment was provided orally rather than in writing; and (f) modes of regulation were not equally distributed across the cyclical phases of regulation, with socially shared regulation being the predominant mode in the forethought phase and self-regulation in the reflection phase. Findings provide insight into students' affective experience of self- and peer assessment. They also shed light on the association of modes of regulation with self- and peer-assessment activities and raise new questions about emotional context and variations in modes of regulation throughout the cyclical phases model of self-regulation.