The COVID-19 pandemic provided a unique opportunity to examine the contributions of social interaction and other non-social factors to loneliness among older adults in the context of confinement measures constraining opportunities for in-person social interactions. This study aims to identify groups of individuals with heterogeneous trajectories of loneliness during the COVID-19 pandemic and to explore the sociodemographic, health, psychological and social interaction-related factors associated with these trajectories. In this 12-month longitudinal study, 614 community‐dwelling individuals aged 60+ years completed telephone-based interviews on four occasions between May 2020 and May 2021. Loneliness was evaluated using the three-item version of the UCLA Loneliness Scale. Multilevel modelling assessed average changes in loneliness over time. Group‐based trajectory modelling was performed to identify distinct trajectories of loneliness over time. Multinomial logistic regressions were conducted to explore the predictors of these trajectories. On average, there was a curvilinear change in loneliness that tracked the stringency of the COVID-19-related confinement measures. In this convenience sample, three heterogeneous trajectories were identified: a stable-low (17.2%), a fluctuating-moderate (48.8%) and a sustained-elevated (34.0%) trajectory. Participants in the sustained-elevated loneliness trajectory were more likely to live alone and experience elevated psychological distress and greater COVID-19 perceived health threat compared to those in the stable-low trajectory. Participants in the fluctuating-moderate loneliness group were more likely to have multimorbidity, experience greater psychological distress, and have less frequent in-person interactions than the stable-low loneliness group. Assessing the combination of sociodemographic, health, psychological and social factors may help identify individuals at higher risk for chronic loneliness.