Vocabulary knowledge has been largely viewed as an important component in language learning and language acquisition. Understanding how EFL learners approach vocabulary learning is also considered crucial for language teachers and researchers to develop an effective learning environment that may stimulate high-quality learning outcomes. Studies on vocabulary size suggest that Saudi EFL learners have impoverished vocabulary knowledge, but there is still little known about how likely certain vocabulary learning strategies may enhance vocabulary knowledge. This study aims to address this issue. We specifically aim to identify the type of vocabulary learning strategies more frequently used among Saudi female EFL learners, and how the use of certain learning strategies may influence vocabulary knowledge. We asked participants to complete two test instruments: the Vocabulary Learning Strategies Questionnaire and the Vocabulary Size Test. All data was gathered using an online survey and the results showed evidence that participants largely rely on metacognitive learning strategies to learn English vocabulary, and all participants seem to have no problems with high- and mid-frequency words. Our relationship tests also suggest that the increase in using the metacognitive strategy is likely to enhance vocabulary knowledge among our participants. These results together are thought to provide useful insights to language learning theories in general and to Saudi teachers and policymakers in particular about how they can help students overcome challenges associated with their vocabulary learning strategies and vocabulary size.