The present article purported to gain insights about English as a second language (ESL) learners’ knowledge of grammatical functions at the declarative and the procedural levels in the higher education context, and argued that the dialogue between the types of knowledge calls for more attention. The study utilised a Words-in-Sentences Test that was administered to 841 ESL students in seven colleges and universities in three Arab countries: United Arab Emirates, Jordan and Oman. The test was used to measure the participants’ declarative knowledge of grammatical functions. The participants’ test scores were then correlated with their essay writing scores to find if there is a significant correlation between the two, and thus gain insight into the relationship between the declarative knowledge and the procedural knowledge of grammatical functions. Finally, a qualitative analysis was conducted on nine essays to gain an in-depth understanding of this relationship. The findings indicated that the university participants’ declarative knowledge of grammatical functions was below the expected level and that there was a significant correlation between the learners’ test scores and writing scores. In addition, intriguing themes emerged from the qualitative analysis. Together, the findings are anticipated to spark more research on grammatical function knowledge among university students in ESL contexts.