Abstract Background Social distancing and isolation during the COVID-19 pandemic left a mark on the social, emotional and cognitive development of youth. We aimed to identify the course of Dutch youth loneliness and its predictors since the Omicron lockdown in December 2021. Methods Data were obtained from a repeated cross-sectional panel study between March 2022 and September 2023, in which loneliness was assessed using the 6-item De Jong Gierveld Loneliness Scale. Youth (12-25 years) participating in at least three timepoints were included. A latent class growth analysis (LCGA) was performed to identify trajectories of loneliness. Themes identified in qualitative data (open-ended questions halfway 2022) were recoded into binary quantitative variables to be included in regression analyses. Two-step multivariable multinomial logistic regression was used to determine risk factors per trajectory class. Goodness of fit was assessed using the likelihood-ratio test. Results Identified trajectories were: 1) very lonely (n = 140), 2) moderate lonely (n = 373), 3) recovering (n = 511), and 4) not lonely (n = 384; reference). Compared to the other trajectories, youngsters following a moderate or very lonely trajectory had more often little to no trust in the future and more often experienced non-specific symptoms and stress due to various causes. Including perceptions showed that youth in these trajectories experienced a greater impact of the pandemic on their social relationships. The inclusion of perception also improved the model’s goodness of fit (p < 0.001). Conclusions Up to 18 months after the COVID-19 pandemic, youngsters that reported loneliness continue to endure its consequences on their social lives. Despite the apparent association between the Omicron lockdown and continuing loneliness, claims about causality should be made with caution. However, findings implicate the importance of political and social recognition of the pandemic’s ongoing impact on vulnerable youth. Key messages • Lonely youth experienced a greater impact of the COVID-19 pandemic on their social lives. • Political and social recognition of the pandemic’s ongoing impact on vulnerable youth is wanted.