Ambiguities are naturally found in languages and largely categorized into lexical and syntactical ambiguities. They are responsible for ambiguous expressions and may cause confusion in readers; therefore, accurate evaluation of them is critical for clear writing which is one of the prominent prerequisites for academic writing. The literature shows that novice writers such as students are those who suffer from ambiguity the most. Accordingly, the present study examined student writing to reveal students' lexical and syntactical ambiguities in their writing and evaluate the result accordingly. The aim of this study is to investigate whether lexical or syntactical ambiguities are more common in student writing, and also to suggest some pedagogical implications for the instructors at higher education to disambiguate expressions. This study collected data from four exams held in 2019-20 fall and spring terms. The results showed that student writing includes more lexical ambiguities than syntactical ambiguities and students are more prone to lexical ambiguities of verbs when compared to other grammatical items.