Introduction COVID-19, also known as Coronavirus disease, was detected in Wuhan, Hubei, China in December 2019. Since then, the virus has been designated a global pandemic, affecting all nations. Nigeria as a whole has recorded 255,937 cases of COVID-19. Studies on COVID-19 anxiety level, knowledge, and attitude have not been focused on youths after the lockdown. This research explored COVID-19-related knowledge, attitudes, and anxiety levels among Nigerian youths after the lifted pandemic lockdown. Methods after the COVID-19 pandemic lockdown, an online descriptive cross-sectional survey was performed among 818 young people aged 18 to 35 in South-Eastern Nigeria. The Statistical Package for Social Science (SPSS) version 25 technique was used to analyze the descriptive statistics. The Chi-square test, bivariate, and multivariate binary logistic regression were used to measure the associations. A p-value of 0.05 was statistically significant at a 95% confidence level. Results the majority of respondents 723 (88.39%) demonstrate a high degree of COVID-19 knowledge. Just a few respondents (0.49%) expressed a negative understanding of the virus. 556 (67.97%) had a positive attitude towards the virus. More than half of the respondents had a low anxiety level, 471 (57.58%) and 108 (13.20%) had a high level. Educational level, place of residence, and family income showed a statistically significant relationship with their anxiety levels (p = 0.001, 0.002, 0.01, respectively). Conclusion the infection, transmission, and symptoms of COVID-19 were well-understood by young people after the pandemic, who also displayed optimistic attitudes and low levels of fear. Higher levels of education, family income, and dwelling location were connected with COVID-19 knowledge and lower anxiety levels. This knowledge will assist health professionals in fighting current and future related outbreaks.