<![CDATA[Although learning motivation, learning interest, vocabulary mastery, and learning independence are recognized as key contributors to EFL speaking development, they are often examined in isolation. This study investigated the direct and indirect effects of learning motivation, learning interest, and vocabulary mastery on English speaking ability through learning independence and identified the strongest predictor of speaking performance. An explanatory quantitative design was employed with 148 undergraduate EFL students selected through purposive sampling. Data were collected using a structured questionnaire and a speaking performance test assessing fluency, pronunciation, vocabulary, grammar, and comprehension. Partial least squares structural equation modeling (PLS-SEM) was used for data analysis. The results revealed that learning interest (β = 0.278, p = 0.002), learning motivation (β = 0.240, p = 0.021), and vocabulary mastery (β = 0.372, p < 0.001) significantly predicted learning independence. Vocabulary mastery (β = 0.309, p = 0.003) and learning independence (β = 0.373, p = 0.001) significantly predicted English speaking ability, whereas learning interest and learning motivation showed no significant direct effects. Learning interest and vocabulary mastery exerted significant indirect effects on speaking ability through learning independence, while learning motivation did not. The model explained 67.4% of the variance in speaking ability and 63.8% of the variance in learning independence. These findings indicate that learning independence is the strongest direct predictor of English speaking ability and a key mediating mechanism linking vocabulary mastery and learning interest to speaking performance. Integrating vocabulary development, learner-autonomy strategies, and sustained speaking practice may therefore enhance EFL speaking outcomes.]]>
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