The recent results of the Education First English Proficiency Index (EF EPI) showed that the country placed seven spots lower compared to the past ranking. The purpose of this study is to determine the level of competence of students in grammar and academic writing and to find out if a significant relationship existed between the variables. This research paper utilized the Descriptive-Correlational research design to determine the level of grammatical and academic writing competence and to determine possible associations between them. The ninety (90) respondents were from the Grade 10 students enrolled in Special Science Class selected using a stratified sampling technique. The researcher-made questionnaire was given to the students through an online platform that has gone through validity and reliability testing. The statistical tools used were the mean and standard deviation to determine the levels of competence, and the Spearman Rank Order coefficient ? was used to determine the relationship between grammar and academic writing competence. The results in the grammar (M=28.29, SD=3.92) and academic writing tests (M=20.37, SD=3.25) revealed that the students are moving towards mastery, likewise, it showed that there is no significant relationship between the grammatical competence and the students' academic writing competence (p-value = 0.3121). Several variables are also measured to determine the influence of these factors, such as sex and parents' educational attainment. This study revealed that the students' sex has no significant difference in the students' level of competence in grammar and academic writing, while the students' parents' highest educational attainment has a significant difference with the students' academic writing competence, especially with parents' that has a post-graduate degree. It can be concluded that the proficiency of the students in grammar does not correlate with their academic writing skills of the students.