The Null Subject Parameter (NSP) has long been considered pertinent to Second Language Acquisition (SLA) studies, especially when the native language (NL) and target language (TL) have different NSP settings. The study aimed to investigate whether seventy English L2 learners in Puerto Rico who were native Spanish speakers transferred their L1 syntax related to NSP to their English production. It explored the patterns and frequency of subject pronoun omission of these learners and examined the potential influence of their L1 on their L2 syntax. The study used questionnaires to assess the participants educational background, NSP awareness, grammaticality judgments of English sentences, and translation skills from Spanish to English. It was found that the majority of English L2 learners in the sample, who had received education in the K-12 public-school system in western Puerto Rico, did not reset the Spanish null subject parameter to the English non-null subject parameter. Many of the proficient-level participants continued to use their Spanish L1 when judging sentences missing overt-subject pronouns and that-trace violations. They also had difficulty translating a sentence missing and overt-subject pronoun related to the weather. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]