This study explored the association between flipped learning readiness (FLR), engagement, social anxiety, and achievement in online flipped classrooms among 200 freshman university students enrolled to an information technology course. The relational screening model was applied in order to reveal associations between variables. The study was conducted in two Turkish state universities. The students were sampled using the convenience sampling method. The data collection tools employed were a demographic data form, the Online Student Engagement Scale, the Online Learners' Interactions and Social Anxiety Scale, the FLR scale, and also achievement tests. Structural equational modeling was employed in the testing of the hypothesized model. Results from the structural equation modeling revealed that engagement and FLR were positively associated with student achievement, whilst there was a negative association revealed between social anxiety and achievement in the online flipped classroom. The study also revealed engagement as the most significant predictor of achievement in the online flipped classroom.