This study examined the influence of language knowledge, metacognitive knowledge and metacognitive strategy use on speaking and listening proficiency. Ninety six freshman and sophomore Iranian university students (male = 6, female = 90) were participated in the study. Two kinds of questionnaire and one language knowledge test were administered. Pearson product moment correlation was applied to find the relationship between the variables and speaking and listening proficiency. Multiple regressions were used to test the variance accounted for language knowledge, metacognitive knowledge, metacognitive strategy use in speaking and listening proficiency. The results demonstrated that all the variables correlated significantly with speaking and listening proficiency. All the variables uniquely contributed to speaking proficiency, however; in case of listening, just language knowledge and strategy use were predictors of listening proficiency. Other findings and pedagogical implication of the study are discussed.