This study investigated the acquisition of English Relative Clauses (RCs) by Malaysian L1 Tamil speakers of L2 English based on the Failed Functional Features Hypothesis (FFFH). The aim was to find out if the Tamil speakers were capable of resetting the parameter of Tamil RCs into the English RC settings. The formation of RCs in both English and Tamil involves wh-movement. However, Tamil also allows the non-movement option which is considered ungrammatical in English. Specifically, the study investigated the development of English RC acquisition among three different proficiency groups of L1 Tamil learners who were selected based on the Oxford Placement Test 2. Data was gathered from 145 students via a Grammaticality Judgement Test. The results showed that the ability of the participants to accept grammatical items was better than their ability to reject ungrammatical items. The results also showed that if two options of a parameter were available in the L1, then one would be the default, and this tended to be carried over to the L2 acquisition process. Thus, the findings showed that the participants’ L2 grammar seemed to lack the functional features involved in English RC formation, which were not accessible after the critical period, supporting the FFFH.