Abstract The present study investigates the acquisition of English articles in relative clause contexts by L1 Kuwaiti Arabic speakers. We propose a testing instrument designed to evaluate the use of the definite and indefinite articles in restrictive relative clauses, focusing on the impact of L1 transfer effects. Specifically, we test four conditions involving definite and indefinite nouns modified by restrictive relative clauses, with or without an overt relativizer “that”. The participants (N = 117) were divided into four proficiency levels, ranging from low intermediate to advanced learners of English, and completed a forced-choice elicitation task with 24 test items. Findings show a facilitative L1 transfer effect in the acquisition of the definite article, with a higher accuracy rate in advanced learners, whereas the indefinite article proved to be a greater learning challenge due to the lack of morphological realization in Kuwaiti Arabic. Optionality, observed in indefinite contexts, highlights the persistent difficulty that L1 Arabic speakers face in acquiring L2 English article distinctions at the syntax-semantics interface. These findings suggest that while learners can converge towards target-like grammar, transfer effects and limited positive and negative evidence in input delay the process, with significant pedagogical implications for ESL teaching in Arabic-speaking contexts.