Language achievement and motivation are essential dependent variables for assessing the efficacy of pedagogical methodologies in language learning. This study investigates the impact of the flipped classroom approach on enhancing language achievement and attitudes towards flipped classroom approach among engineering students at an Aeronautic University in Tehran, Iran. Employing a quasi-experimental research design, the study involved 40 senior and first-year students, aiming at improving their English language proficiency and finding their views and attitudes towards the flipped classroom approach. Data collection included surveys and quantitative questionnaires, classroom assessments. Results from the analysis of covariance (ANCOVA) (F(1, 37) = 13.31, p = .001), revealed that applying flipped classroom approach boosts ESP learners’ language achievement. Additionally, the flipped learning questionnaire results showed high student motivation (t = 4.96, p = .000), and effectiveness of flipped learning (t = 4.84, p < .000). These findings showed the usefulness of flipped classroom model as an effective strategy to enhance language achievement and learner motivation, offering valuable insights for educators in diverse educational settings.