This quasi-experimental mixed-methods study investigated the structural impacts of cooperative versus competitive gamification on vocabulary collocation mastery and Foreign Language Classroom Anxiety (FLCA) among EFL English majors. A sample of 147 undergraduate students was divided into a cooperative gamification group (n = 74, utilizing Quizizz Team Mode) and a competitive gamification group (n = 73, utilizing Quizizz Solo Mode) over a six-week instructional period. Data were gathered using parallel collocation achievement tests administered at three intervals, a modified FLCA questionnaire, and weekly reflective journals. Split-plot ANOVA results revealed that while both mechanisms facilitated similar immediate post-test performance, the cooperative group demonstrated significantly higher long-term lexical retention on the delayed post-test. Furthermore, t-tests indicated that cooperative gamification dramatically mitigated classroom anxiety, whereas competitive gamification significantly intensified students' fear of negative evaluation and public performance pressure. Qualitative data corroborated these trends, revealing that cooperative structures fostered an environment of psychological safety and shared accountability. The study concludes that theory-driven, cooperative game designs are vital for balancing cognitive mastery and affective well-being in tertiary EFL education.