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This study explores the relationship between metacognitive awareness and 2 aspects of vocabulary knowledge (i.e., declarative versus skill) in “more explicit” and “less explicit” language learning groups. Also, it investigates whether declarative aspect, operationalized in vocabulary size, and skill aspect, operationalized in the productive use of vocabulary, differ in the more explicit and less explicit language learning groups.  To these ends, 80 Iranian EFL learners, majoring in English Translation at Shahrekord and Esfahan Payam-e-Noor Universities were selected through Oxford Placement Test. Schraw’s (1994) Metacognitive Awareness Test was used to measure the participants’ degree of the explicit knowledge Nation’s (1990) Vocabulary Levels Test and Laufer and Nation’s (1999) Productive Vocabulary Levels Test were also used to measure their skill and declarative knowledge, respectively. Correlational statistics indicated a significant and positive correlation between metacognitive awareness and declarative knowledge, but a significant and negative correlation between metacognitive awareness and skill aspect of vocabulary.  Moreover, t tests indicated that the more explicit group was better in the declarative aspect whereas the less explicit one was better in the skill aspect of vocabulary knowledge. The findings shed light on the cognitive dimension of vocabulary learning.