Filipinos have stood apart from their contemporaries from other parts of the world because they read, write, listen and speak the lingua franca of the global arena. This may have been the scenario a decade ago but the same cannot be said for the present. This study sought to determine the factors that mostly affect the grammar proficiency of students, in order for educators to take these indicators into consideration in designing strategies for use in the English classroom. This study used the descriptive correlation research method, since it aimed to describe the level of the respondents’ grammar proficiency, depending on their choice of reading materials, communicative environment and language transfer skills from native to target language. Results revealed that the said factors have no significant influence on the level of grammar proficiency among the respondents. The researchers recommended that teachers of English language subjects clarify to their students the differences of sentence structure in the English language with that of commonly spoken languages or dialects in order for their students to take this knowledge into account when they are transferring their thoughts and ideas from their mother tongue to English.