There has long been a widespread belief that academic writing has to maintain a high degree of formality and impersonality. Despite this, it has been observed that there is a general tendency to use informal style in academic writing by writers from different disciplines. This informality manifests itself in the use of various linguistic devices that were previously observed only in spoken discourse or in informal communication. The aim of the study is to identify common informal features in English academic writing used by Arabic and British scholars and compare the level of informality used in English academic writing by representatives of the two lingua-cultures. The study adopts the corpus linguistics method. The one-million-word Arab Scholar Written English Corpus (ASAWEC) was compiled and analysed for informality features. The results were then compared to the British Academic Written English (BAWE) corpus. We focused on the use of informal features, such as broad references, initial conjunctions, first-person singular, second person pronouns, final preposition, listing expressions, split infinitive, and contractions. The results revealed a significant difference in the use of informality features in favour of the native speakers. The findings showed that Arabic scholars tend to use broad references and initial conjunctions, however, they rarely use contractions and split infinitives. Contrary to this, British scholars used the whole spectrum of informality features. The findings can provide insightful implications for researchers, journal editors and peer reviewers to account for informality levels in academic writing in different linguacultures. They may also be used in teaching English academic writing.