This research studied the effect of integration of information and communication technology (ICT) in classroom for enhancing 21st century learning skills which included collaboration, communication, information literacy, media literacy, and ICT literacy. In this study, based on learning theories and student-centered approach, integration of ICT included four effective functions; dynamic content presentation, information access, creation and sharing, interaction and reflection. Seven educational technology experts evaluated these functions by an assessment tool. The evaluation showed that the integration was appropriated. The integration was then applied into teaching and learning process throughout the course to study the effect. 69 undergraduate students and 22 graduate students in two different 4-months courses were target studied. The students were assessed themselves by a 21st century learning skill assessment tool before and after courses. The results showed that integration of ICT in classroom could enhance the 21st century learning skills for both undergraduate and graduate levels significantly with high effect size.