The COVID-19 lockdowns are reported to have negatively influenced the wellbeing and learning efficacy of students. In this context, we analyzed the psychological impact of the COVID-19 quarantine on healthcare students, a subpopulation experiencing high stress levels. Our survey-based, cross-sectional study assessed wellbeing indicators, lifestyle and learning behaviors before and during the quarantine for 388 Romanian healthcare students. Our findings included the increase in phone and social media use, at the expense of formal and independent study time; deteriorations in mood, self-organization capacity and learning efficacy, and increased procrastination behaviors. Unexpectedly, our study identified an improvement in sleep quality and duration. The increase in social media use was less severe among rural students. We identified correlations between study time, online activities (including social media), wellbeing indicators and procrastination. Our study draws attention to quarantine-induced deteriorations of wellbeing and learning capacity in an important category of students.