This study investigated the relationship between language learning strategies and achievement among Yemeni EFL university students. It also identified the differences between high and low achievers in using language learning strategies. Seventy students were randomly selected from the fourth level on the basis of their university scores as high and low achievers. The study adopted the SILL questionnaire developed by Oxford (1990) to collect the data of the study. The obtained data were statistically analyzed through SPSS software. The results of the study showed that the most frequently used strategies of high achievers were meta-cognitive, compensation and cognitive strategies while the least frequently used strategies were affective, memory and social Strategies. On the other hand, the most frequently used strategies of low achievers were meta-cognitive strategies, the strategies entitled "Others" and affective strategies whereas the least frequently used strategies were cognitive, social and memory strategies. The findings also revealed that there was a statistically significant difference between high and low achievers in the overall use of LLSs in favor of high achievers, there were significant differences between high and low achievers in using meta-cognitive, compensation and cognitive strategies in favor of high achievers and there was a positive relationship between the overall use of language learning strategies and students' academic achievement. It was also found that the meta-cognitive and compensation strategies positively correlate with the students' academic achievement. The findings have significant implications for research on LLSs, classroom instruction, materials design, and teacher preparation.