In ESL and EFL contexts, prepositions are notoriously difficult for English language learners to master due to many reasons. This study attempts to explore the difficulty of learning and using English prepositions correctly by Moroccan 2nd-year baccalaureate students, and analyzes the common types of errors (substitution, addition, omission). Also, this study investigates the extents to which interlingual and/or intralingual transfers constitute the main source of prepositions errors. This study was conducted at Abi Hayan Taouhidi High school in Kénitra-Morocco. During a month long internship, the data was collected via classroom observations and a written test that was administered to a sample of 60 students. The findings of this research show that English prepositions errors in this context can be attributed to various factors such as: the large number prepositions in English, the polysemous nature of prepositions, the complexity of the preposition system, the lack of rules of usage in most cases, the use of prepositions in context differs immensely from one language to another, and the absence of an effective method to teach correct the prepositions usage.