This research investigated on the first language interference in learning the English language among three cultural groups -- the Ilocano, the Ibanag, and the Itawes. The subject of the study were sixty sophomore students from the College of Education and the College of Business Entrepreneurship, and Accountancy who are officially enrolled at Cagayan State University, Andrews Campus, Tuguegarao City for the school year 2010-2011. This research ascertained that the students, regardless of their ethnic affiliation, had similar proficiency levels in the written proficiency test. The students did not do well in the oral test, specifically on intonation and pronunciation. They had several errors in their performance and that their first language, to a great extent, interfered with their English language learning. However, the students' L1 facilitated in the completion of a given task on speaking. The students had to turn to their L1 in some instances. Their first language, therefore, served as a mechanism or strategy to realize an objective in language learning. On the other hand, while the researcher believed that the L1 serves to facilitate in learning the L2 and that the students should be allowed to use their L1 in the English language classroom, she stressed that teachers can strategize to provide students with opportunities to practice their speaking skills in the target language. The researcher also emphasized that this study becomes a basis for constructing a prototype remedial instructional module for learning speaking particularly on intonation and pronunciation focusing on contrast analysis of patterns of intonation and sound production between L1 and L2.