The research on the effects of metacognitive strategy awareness and self-regulation on second language reading achievements has come to confirmatory conclusions. However, the associations and possible interactions between metacognitive and self-regulatory capacities have been subject of debate. Theoretically, the relationship between the two global skills in affecting learning has ranged from rivaling alternatives to complementary associates. Accordingly, some recent perspectives have delineated the relative potency of the two concepts within models where metacognitive, behavioral, motivational and emotional dimensions of learning interact. This study resorted to structural equation modeling in outlining and testing the causal relationships between three types of metacognitive reading strategies, namely global, problem-solving, and support strategies, and self-regulation in affecting reading proficiency. The data were collected from 311 Iranian undergraduate students majoring in English using Metacognitive Awareness of Reading Strategies Questionnaire, Self-Regulation Questionnaire and reading proficiency test. By testing the hypothesized model against several fitness criteria, the causal relationships among the variables were confirmed indicating a positive relationship between three components of metacognitive awareness and reading proficiency by mediating role of self-regulation. The findings provide further conceptual support for dynamic models of self-regulated action and practical implications regarding the complementary role of metacognitive and self-regulatory engagements in reading development.