Over the past decades, an abundance of studies have assessed teacher attitudes and self-efficacy beliefs related to inclusive education. However, empirical evidence on the causal relationship between efficacy and attitudes is still rare and inconclusive. Therefore, the present study focused on identifying the interdependent relationship between teachers' attitudes and their self-efficacy beliefs using a cross-lagged panel design path analysis. A total of 1326 teachers from Finish schools participated in an electronic survey. Teachers' self-efficacy beliefs were assessed five times and attitudes (attitudes and concerns subscale) three times over three years. The outcomes indicated that both constructs are relatively stable over the measured period. Moreover self-efficacy had a positive effect over time on both types of attitudes but not vice versa. This cross-lagged relationship was stronger between efficacy and concerns. These results were similar between male and female respondents and between novice and expert teachers. This implies that increasing teacher efficacy for inclusive practices is likely to change their attitudes toward positive direction. Implications for developing inclusive education and teacher education are discussed.