Primary school students rely heavily on textbooks for instruction. Using the variety of textbooks, a description of the theme textbooks' linguistic quality is conspicuously absent, particularly for students in the fifth grade. Language fit for students' growth, communicative language, and coherence and cohesiveness were all included in this study's analysis of textbooks' language quality. Qualitative content analysis was used in this study's methodology. All texts from the heat and transfer-themed of fifth-grade textbooks published by the Indonesian Ministry of Education and Culture, Yudhistira, and Erlangga publishers were included in the study. Documentation was utilized to collect the data. Sample, record, reduce, infer, and narrate were all data analysis approaches used. The findings of this research indicated that the three publishers' textbooks had excellent language quality in terms of language compatibility for students' growth and the communicative language issued by the Indonesian Ministry of Education and Culture and Erlangga was wonderful, but Yudhistira was awful. There were a lot of solid points made in the Ministry of Education and Culture's publications. Both Yudhistira and Erlangga performed admirably. The quality of textbook language was found to be satisfactory in this study.