From a holistic perspective of positive psychology, there is a dearth of knowledge regarding how its three underlying factors (i.e., positive subjective experience, positive individual traits, and positive collective institutions) co-shape learners' willingness to communicate (WTC), a critical facilitator of foreign language learning achievement. This research gap is particularly evident for learners in multi-ethnic regions who have been underrepresented in foreign language education in China. This issue may constrain our understanding of the contributions of positive psychology to the field of applied linguistics, since the role of positive psychological factors in influencing WTC may be distinct across diverse ethnic populations. Besides, the relative importance of these three factors in predicting WTC has yet to be investigated in latent models. Given that different pedagogical approaches may engender disparate perceptions and attitudes among learners, it is of the utmost importance to ascertain which factor should be prioritized in classroom psychological interventions, as well as in teacher training programs. To address these gaps, this study addressed the joint effect of positive subjective experience (foreign language peace of mind, FLPOM), positive individual trait (language-specific grit), and positive collective institution (classroom environment) on WTC using structural modeling analysis. Furthermore, the study employed latent dominance analysis to ascertain the relative importance of these three factors in promoting WTC. The sample consisted of 643 multi-ethnic foreign language students from five provinces in Western China. The findings suggested that FLPOM, grit, and classroom environment collectively stimulate learners' WTC. Notably, FLPOM, a factor that has not previously been examined in relation to in-class or face-to-face WTC, emerged as the most statistically significant predictor of WTC. Therefore, it is imperative that foreign language practitioners and learners recognize the significance of FLPOM in language learning and teaching in Chinese multi-ethnic regions.