The purpose of this research is to examine the effects of formative assessment practices on students' academic achievement, attitudes toward lessons, and self-regulation skills in the fifth-grade social studies class. Mixed method research was used to conduct the study. The research group consisted of 45 students in the fifth grade of a secondary school in Erzurum in the academic year 2014-2015, and a teacher who performed the practices. Experimental procedures were carried out for 28 weeks. Social studies performance tests, attitude inventories for social studies classes, self-regulatory learning skills scales, semi-structured interview forms, and observation forms were all used as data collection instruments. As a result of the research, it was determined that the experimental group in which the formative assessment practices were performed had a significantly higher academic achievement levels and better attitudes toward the class than the students did in the control group. With regard to the students' self-regulation skills, although the formative assessment had a positive effect, no significant difference was found between the experimental and control groups. According to the researcher' s observations and the interviews conducted with the teacher and students, it was determined that the general view on the application of formative assessment was notably positive.