The purpose of this study was to assess the causal association of the writing proficiency of students as viewed from the context of writing strategies’ utilization and writing motivation among first-year English major students of Teacher Education Institutions in Region XI. The study used an explanatory sequential mixed methods design. The quantitative strand utilized an adopted survey questionnaire distributed to 300 respondents while the qualitative approach employed 17 informants from among the 300 respondents through purposive sampling. Ten were subjected to IDI and seven to FGD among the 17 participants. The study revealed that writing strategies’ utilization of respondents indicated high level in metacognitive, effort regulation, cognitive, social and affective strategy. Moreover, students perceived a high level of writing motivation in terms of intrinsic, extrinsic and self-regulatory. Also, students have high level of writing proficiency in terms of attitudes towards writing, generating, revising, feedback, and awareness and control of the writing process. All variables were found to have a significant influence on writing proficiency. The participants of the qualitative strand agreed with the quantitative results. Hence, the nature of data integration was revealed to be connecting-confirmation.