The purpose of this study is to examine reflections of the design process of the Rube Goldberg machines on prospective science teachers' STEM awareness. A mixed design approach was opted for in this research. Data were obtained using learning diaries and a STEM awareness scale. Quantitative data was analyzed using a paired samples test. Content analysis was also used for dealing with the qualitative data. The results showed that, based on the findings obtained from both forms of data, Rube Goldberg machines have a positive influence on the STEM awareness of prospective science teachers. The prospective science teachers who took part in this research explained that Rube Goldberg machines are particularly effective in learning science concepts related to simple machines, although it was not one of the purposes of this research. Consequently, future research could be conducted to examine the effectiveness of Rube Goldberg machines in learning basic science concepts related to simple machines.