Motivation to learn science positively affects students to become science literate individuals. Therefore, researchers have conducted many studies to determine the factors that increase students' motivation. Most of these studies have focused on various teaching methods and techniques' effects on students' motivation. However, in contrast to the abundance of studies conducted for this purpose, there are very few studies on the knowledge and practices of teachers and preservice teachers on motivation and motivating students. Therefore, this study aims to examine the knowledge and practices of preservice science teachers in motivating students to learn science by using a case study. The participants consist of eight preservice science teachers attending the fourth grade at a state university in Turkey. Interviews, lesson plans, and presentations were used to obtain data on the quality of participants' knowledge and practices about motivating students. The interview data were analyzed by content analysis and coded into categories. The qualities of the teaching practices included in the lesson plans and presentations regarding motivating the students were analyzed using Keller's ARCS model. The findings showed that preservice science teachers' knowledge was far from reflecting the motivation's multidimensional nature. Additionally, findings revealed that preservice science teachers mostly defined motivation as attracting interest and attention, and in line with these views, the practices they planned to use to motivate students were mostly classified under the category of generating and sustaining the attention of the ARCS model. Suggestions are made to increase the knowledge and practices of preservice science teachers about motivation.