In this study, the effects of teaching the 10th grade students the subject of probability through lessons prepared via Understanding by Design (UbD) on their probability success levels and attitudes and also the students' views about this process were examined. The study was designed as an embedded experimental model. The students' attitudes towards probability were measured through the scale developed by Bulut (1994) and their success levels were measured by the achievement test developed within the scope of the study. The students' opinions were collected through individual interviews. Based on the analyses, it can be stated that although the teaching practice increased the experimental group's success level significantly compared to the pretest, it did not make a significant difference in the post-tests compared to the control group; however, it increased the attitude level of the experimental group significantly compared to both the pretest and the control group. Moreover, the students stated positive opinions about the way of teaching the course and its contribution to lessons and also emphasized the importance of probability in decision-making.