During the COVID-19 pandemic crisis, the experience of quarantine has been an undesirable condition for people and it can have a negative impact on mental health and psychological wellbeing. Social isolation has led to an increase in time spent on social network sites, with people interacting more frequently with each other, and comparing online the way in which they are experiencing the same state of home confinement. Our study aimed to investigate the role of online social comparison on individuals' psychological distress and life satisfaction during the COVID-19-related quarantine. Specifically, a cross-lagged panel study at three-waves was conducted in Italy in order to examine the change in psychosocial distress levels (e.g. depression, anxiety, stress, loneliness, low life-satisfaction) from before the quarantine for a period of one month, as well as the predictive role of online social comparison to ameliorate individual distress. An online survey was distributed through a social media platform three times after the initial lockdown and at the epidemic's peak two and five weeks later. A total of 113 participants participated in an online survey between the 7th of March and 14th of April 2020. The results showed an increase in the levels of loneliness, depression, stress, anxiety and a decrease in the level of life satisfaction in the pre/post quarantine comparison. Our cross-lagged results also showed that online social comparison at T1 and T2 predicted the individual's improvement in levels of anxiety, stress, loneliness and life satisfaction over time. Overall, the results of the current study underline the positive effects of online social comparison on the reduction of psychological distress during the COVID-19 quarantine.