There is a consensus among mathematicians and mathematics educators that creativity plays an essential role in doing mathematics. Creative students are self-regulated students who take control over processes and experience high self-efficacy beliefs. The aim of this case study was to promote mathematical creativity and self-efficacy of elementary students through a collaborative research task, and qualitatively elicit their efficacy-beliefs about performing creative mathematics tasks. The research questions asked about the students' ability to show creativity in the classroom and about the extent to which the task enriched their mathematics knowledge, and made them realize the beauty of mathematical creativity. Participants were 24 sixth graders who attended a college of education once a week, to learn mathematics. This study revealed the potential of student engagement in creative mathematical work that demanded meta-awareness, self-regulation, and self-efficacy. As the confidence to work mathematically was communicated by their peers, many students expressed a change in their attitudes to their own mathematical competence and were more willing to engage with unknown or challenging mathematical tasks. The contribution of this study is twofold: finding ways of developing the students' creativity and enhancing their performance, and engaging them in an activity that made them realize the beauty, wealth, and elegance of mathematics, thus enhancing their self-efficacy to learn mathematics. We recommend providing students with opportunities to enhance their mathematical creativity by using creative tasks.