The aim of this study is to investigate the association between alexithymia and online gaming addiction in adult MMO game players, employing structural equation modeling. Specifically, it focuses on relationships between core components of alexithymia (difficulty identifying feelings, difficulty describing feelings, externally oriented thinking) and two forms of excessive gaming – pathological gaming addiction and non-pathological high engagement. The study also examines factor validity of the Czech version of the TAS-20 scale for measuring alexithymia, whose psychometric properties have not been systematically evaluated yet. The study is based on the analysis of the data from a three-wave longitudinal survey among online players, which was realized during years 2013-2014 as a part of GAČR project Nové behaviorální závislosti at the Faculty of social studies. The sample consisted of 1482 Czech and Slovak MMO game players (1371 men, 111 women) aged 20-69. The data were collected using self-report questionnaires distributed on gaming discussion forums, online gaming magazines and on gaming community websites. Using the confirmatory factor analysis, the original 3-factor structure of the TAS-20 was not supported. For further analysis, the alternative model was used taking into account the reversed item bias. In the final structural model, online gaming addiction was positively predicted by difficulty identifying feelings and externally oriented thinking, while engagement was negatively predicted by externally oriented thinking. Remaining relationships were nonsignificant. It was also found that both online gaming addiction and engagement are slightly decreasing with age and conversely increasing with higher frequency of gaming. Thus, this study supports the importance of the distinction between actual gaming addiction and excessive but non-pathological gaming.