Under the traditional English learning context, English as a Foreign Language (EFL) learners have few opportunities to apply their knowledge to a real-life setting. According to situated learning theory, different contexts hold different concepts related to learners’ real experiences. The researchers, therefore, integrated drama activity into EFL learning with the support of mobile devices to create an authentic English learning environment. In this study, the researchers developed a mobile-based system named Collaborative Contextual Drama (CCD) which provides the learners with text/picture annotation and drama-making for the purpose of fostering their English learning in authentic contexts. A goal of this study is to examine how CCD, with contextual English drama activities, influences learners’ learning behaviors as well as learning achievements. The post-test revealed that the learners who learned with CCD in familiar authentic contexts could significantly improve their English compared to the learners who learned without CCD. Furthermore, delayed tests revealed that the learners who learned with CCD could retain their knowledge longer. In addition, regarding learners’ behaviors and drama performances, it was revealed that intonation, quantity of annotations they made, quantity of interactions with environment, and quantity of using physical movement significantly affected their EFL learning achievement.