Nowadays, knowing one or more foreign languages is seen as a necessary skill with English being the most spoken and learnt language in the world. Language acquisition involves the acquisition of the basic language skills, the most demanding being the writing skill which can cause significant problems to both native and non-native speakers. Something that will always be a part of language acquisition are errors which are today seen as inevitable and positive elements of the language learning process. The aim of this paper was to indentify what language errors students make while writing in English and what are the causes of such errors. 69 students from the University of Zadar, Department of Teacher Education Studies in Gospić participated in the research. Their task was to write an essay on „The position of the Croatian and/or English language in the process of globalisation“. After conducting a quantitative and qualitative error analysis, the results show that the students tend to make more intralingual than interlingual errors thus making the most errors in the use of articles, prepositions and in spelling. It has also been found that the mother tongue, although not the main source of errors, influences the process of writing in English.