There is a large literature on the types of classroom dialogue that are theorised to be productive for learning; however, there is very little evidence for whether these forms of dialogue are more common, applicable or impactful in certain subjects. This mixed-methods study explored how dialogue unfolds in different curriculum contexts. Classroom dialogue was examined through naturalistic observations of English, mathematics and science lessons involving children aged 10–11 in primary schools in England. The Cambridge Dialogue Analysis Scheme (Vrikki, Wheatley, Howe, Hennessy, & Mercer, 2019) was used to investigate the frequency of key dialogue features in 72 lessons. Statistical analysis identified that reasoned dialogue is more frequent in mathematics and both English and mathematics have a proclivity towards more elaborated dialogue (clarifying/building on ideas) in comparison to science. Furthermore, relationships between student attainment and subject dialogues were examined in 63 lessons through multi-level modelling, revealing that elaboration of own and others' ideas (in conjunction with reference to the wider context) in English was associated with student attainment in reading and spelling, punctuation and grammar. No other significant associations between subject dialogues and student attainment emerged. The findings have highlighted that teacher professional development on dialogue should be sensitive to the disciplinary context.