This study examined the antecedents and effects of foreign language enjoyment (FLE) and foreign language learning boredom (FLLB) in synchronous online English courses. Using a mixed-methods design, it delved into first-year English major undergraduate students' first online learning experience. Surveys, short essays, and records of students' grade point averages (GPAs) were used to collect data at the end of the students' first online academic term. The data analysis involved exploratory factor analysis (EFA), correlation, regression, and thematic analysis, guided by previous studies. The findings revealed that students' enjoyment in online English classes was significantly affected by teacher and peer support, class satisfaction and personal pride, learning atmosphere, and personal feelings, while their boredom was generated by disengagement and learning duration. Their effects on online English learning outcomes were both positively and negatively significant, eliciting some pedagogical implications for online English teaching and learning.