This mixed-methods study looks at how intrinsic, extrinsic, and self-regulated motivation affect speaking performance in EFL students at Dong An Polytechnic as they learn the language. A questionnaire comprising modified subscales from Gardner's Attitude/Motivation Test Battery (AMTB) and the validated Vietnamese Version of the Self-Regulated Motivation for Improving Speaking English as a Foreign Language (VV-SRMIS-EFL) was used to gather data from 120 non-English major students. A rubric aligned with the CEFR was used to evaluate speaking proficiency. Additionally, 15 participants who were purposefully chosen for the study participated in semi-structured interviews that yielded qualitative information about the motivational strategies and orientations of the learners. The most common motivator, according to the findings, was instrumental motivation, which was based on practical objectives like career and academic success. However, integrative interests and intrinsic enjoyment also made significant contributions to engagement. Speaking performance was most strongly correlated with self-regulated motivation (r =.52), followed by instrumental motivation (r =.42) and integrative motivation (r =.31). The significance of affect regulation, task value activation, and peer support in maintaining speaking effort and confidence was highlighted by the qualitative results. The study comes to the conclusion that improving speaking proficiency in EFL contexts requires developing self-regulatory capacity in addition to providing pertinent instrumental and integrative opportunities. Future research directions and pedagogical implications are discussed.