The main purpose of the current research was to explore the relationships between beliefs/knowledge and technology integration (TI) during teaching practice (i.e., placement or practicum) among Indonesian pre-service teachers. Five core variables of the theory of planned behavior or TPB (subjective norms, attitudes, perceived behavioral control, behavioral intention, and behavior) and one extended variable, technological pedagogical and content knowledge or TPACK, were included in the proposed model. Data from 1,181 respondents were analyzed through the systematic steps of partial least square structural equation modeling (PLS-SEM) and importance-performance analysis (IPMA). The main findings support all hypotheses; the strongest relationship emerges between behavioral intention and behavior, while the weakest correlation was between TPACK and behavioral intention. All variable performances were satisfactory. The highest performance was attitudes (71.734); the lowest was TPACK (65.027). Broadly, the results indicate the greater importance of beliefs as opposed to knowledge in influencing behavior in relation to TI.