This study aims to explore relationships between non-English majors’ instrumental motivation, interest, and their learning behaviors in a Korean EFL context. Two questionnaires of instrumental motivation and interest were administered to 113 freshmen who were enrolled in a language certificate program for non-English majors. Three of the respondents were invited to a semi-structured interview for in-depth understanding of their perceptions about the program and learning. Results of factor analysis showed the validity of the Promotional and Preventional Instrumentality and the Course and Task Interest as important factors. Pearson correlation and regression analysis were carried out on the data. Results showed that the instrumental motivations were positively correlated with the interest factors and learning behaviors. While instrumental motivations were predictors for learners’ intended effort, learners’ interest in course predicted their achievement test score. The findings suggest that characteristics of context and strong obligations of non-English majors might affect their motivation, interest, and learning behaviors. Limitations and implications of the study were also discussed.