The purpose of this study was to test a model of causal relationships of family communication patterns (conversation and conformity), metacognition and personality traits (openness to experience and conscientiousness) with critical thinking disposition mediated by epistemic beliefs of female high school students in Ahvaz in 2016. The sample consisted of 402 high school students, who were selected by a multi-stage random sampling method. In this study, five questionnaires were used for collecting data, Family Communication Patterns of Koerner and Fitzpatrick, Metacognitive Awareness of Schraw and Dennison, NEO Five-Factor Questionnaire, Epistemic Beliefs of Bayless, and Critical Thinking Disposition of Ricketts. The structural equation modeling (SEM) method was used for analyzing the data. The results showed that all the path coefficients were statistically significant. The relationships of conversation, metacognition, conscientiousness, openness to experience, and epistemic beliefs with critical thinking disposition were positive and significant, and the relationship of conformity with critical thinking disposition was significant but negative. The model fit indices showed that the model fitted the data properly (CMIN = 273.649, df = 50, CMIN / df = 5.473 (P <.001), GFI = .90, AGFI = .83, NFI =.91, IFI = .92, TLI = .89, CFI = .92, NFI = .91, and RMSEA = .09). The indirect paths were also tested using the bootstrap procedure of Preacher and Hayes. The results indicated that all the indirect hypotheses had been confirmed.