The aim is to identify impacts of the differentiated instruction implemented in the primary school fourth grade science course in attitudes of the students towards the course. The mixed method-designed and carried out research was conducted with 9-10 aged students in fourth grade in a primary school in Bilecik during 2015-2016 Spring semester. Quantitative data were obtained with the science attitude scale and quantitative data were obtained with observations, student diaries and interviews with students and teachers. Quantitative data were analysed using descriptive statistics and t test, qualitative data were analysed using the content analysis. Finally, a statistically significant difference was observed between the groups in favour of the experimental group comparing post-test scores of the experimental and control groups obtained from the attitude towards the course scale. As for the qualitative data, findings indicated that the differentiated instruction improved attitudes of the students towards the course. Various recommendations are suggested.