This study aims to investigate difficulties face Saudi EFL students in learning and understanding English idioms, and examines the strategies they utilize to understand idioms. The subjects were 85 male and female Saudi English major university students at the Department of English in Aljouf University. Two data collection instruments, questionnaire, semi-structured interview were employed as well as the Nation's Vocabulary Level Test to measure the students' language proficiency level. The results showed that students have difficulty to understand idiomatic expressions. Moreover, the findings revealed that most frequently used strategies were guessing the meaning of idioms from context, predicting the meaning of idioms, and figuring out an idiom from an equivalent one in their mother language. Furthermore, the results illustrated that low-proficiency students face more difficulties than high-proficiency students, though the differences were not significant. The results also showed that, the greater the vocabulary knowledge, the greater the use of idiom-learning strategies, especially for idioms that require a wider knowledge in vocabulary. This study concludes with teaching implications and recommendation for further research in learning and understanding idiomatic expressions.