The Short Warwick-Edinburgh Mental Well-being Scale (SWEMWBS) is effective in assessing positive aspects of mental health. Despite its advantages, little is known about group differences in the interpretation of SWEMWBS items across age groups, especially during the adolescence period. Hence, this study examined the psychometric properties of the SWEMWBS through Confirmatory Factor Analysis (CFA), Rasch analysis and network analysis of Swedish adolescents during the COVID-19 pandemic. A total of 5548 participants from the south of Sweden (i.e., Jönköping County) took part in this cross-sectional study through an online platform between September 2020 and October 2020. The CFA, Rasch (including differential item functioning, DIF) analysis and network analysis were used to examine the psychometric properties and measurement invariance of the SWEMWBS. The SWEMWBS had a unidimensional structure with robust psychometric properties. The CFA demonstrated measurement invariance across gender, school year and country of birth, which was also confirmed by Rasch DIF. Furthermore, considerable associations between the items of the SWEMWBS, general health and COVID-19 impact items were observed in network analysis. The SWEMWBS showed robust psychometric properties capable of assessing positive aspects of mental health and well-being among adolescents.