This paper explores the relationship of teachers' intelligence beliefs and classroom instruction, in particular teachers' use of intelligence language. According to Dweck's (1999) theory of intelligence, individuals can hold intelligence beliefs on a continuum from an entity theory, where intelligence is fixed, through to an incremental theory, with intelligence understood as malleable. Some research demonstrates congruence between teachers' beliefs and practice; for example, teacher intelligence beliefs and praise language (Lin-Siegler, Dweck & Cohen, 2016). Other findings, however, report incongruence between the belief-practice relationship, such as intelligence beliefs and use of challenge (Rissanen, Kuusisto, Hanhimäki & Tirri, 2018a). Consequently, this study aims to further understand teachers' belief-practice relationship in the classroom. Pilot data were collected through mixed-methods, consisting of Dweck's (1999) intelligence theory questionnaire, video-recorded observations, and semi-structured interviews. Data were analysed using thematic analysis. Findings indicate that the belief-practice relationship is both congruent and incongruent; as teachers' intelligence beliefs are not always enacted during instruction. Rather, intelligence belief and practice may be mediated by other personal beliefs and contextual factors, such as pre-determined target grades, class sets (low, mid, high), beliefs about students and student behaviour; however additional evidence is required.