Interaction in the classroom plays the key role for cultivating students’ 21st century skills. Insufficient breadth of interaction, uneven interaction opportunities, and chaotic interaction existed in many classrooms. With the integration of technology into education, many smart classrooms were built, with one of the aims being to promote interaction. However, the differences of interaction behaviors and engagement in a smart class versus a traditional class could rarely be found in literature, especially with the same teacher lecturing in both classes. In this study, a quasi-experiment was conducted by one experienced English teacher lecturing in a smart classroom with students and a traditional classroom with students for one semester. Research data were obtained by coding the 8 class videos with the proposed “Classroom Interaction Analysis Framework” and the adapted engagement questionnaire, and the data were analyzed using SPSS 24. Results showed that there were no significant differences in either interpersonal interaction or human–technology interaction; however students experienced significantly more engagement in the smart classroom. The reasons were analyzed and interaction patterns in smart classroom were discussed. Finally, a smart classroom interaction model was proposed to promote classroom interaction by considering the interplay of pedagogy, space, and technology.