We examined the longitudinal relationship between teachers' affective attitudes towards inclusive education, subjective norms about inclusive practices, self-efficacy, intentions to use inclusive practices, and their inclusive practices. The study used Ajzen's Theory of Planned Behaviour (TPB) and focused on two domains: personalised instructional practices and collaboration and assessment practices. We analysed longitudinal survey data consisting of responses from Finnish basic education teachers (N = 783) to two questionnaires launched in September 2022 and April 2023. The data on affective attitudes, subjective norms, self-efficacy, and intentions originated from the first round of data collection, and the data for inclusive practices were obtained from the second round. The structural equation modelling (SEM) analysis revealed that teachers' self-efficacy for inclusive practices and their intentions to use inclusive practices significantly predicted their inclusive practices. The positive indirect effects of teachers' affective attitudes towards inclusive education, subjective norms about inclusive practices, and self-efficacy on their inclusive practices via their intentions were statistically significant. This finding demonstrated that teachers' intentions served as a mediator between these three factors and their inclusive practices. The results have significant implications for enriching teacher training programmes, shaping future policies on inclusive education, and improving more inclusive educational practices in schools.