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.