Background: Creativity should be a key issue in mathematics learning. However, mathematics class rarely provides opportunities for students to experience it. Problem solving and posing can play a leading role in promoting creative thinking in mathematics. Objectives: This study aims to have an insight into 6 th -graders understanding of problem solving and posing, analyse their solving strategies, their ability to pose problems, and their difficulties when doing so. Design: Qualitative methods were used in a case study approach. An intervention of five sessions comprising five problem-solving and four problem-posing tasks was implemented in mathematics class. Setting and Participants: Participants were thirty 6 th -graders (11-12-year-olds) from a public supported school in Braga (Portugal). Data collection and analysis: Data collection used photographs, audio recordings, students' written productions, and researcher field notes. Results: Students conceptualised strategies such as building schemas and tables, solving from the end to the beginning, making attempts, and reducing to a simpler problem. Students faced problem posing positively, creating problems adjusted to the requirements, with a wide variety of creative contexts. Students' difficulties in problem solving rely on the interpretation of statements, recognition of previous similar problems, and mathematical communication; on problem posing, difficulties regarding the complexity of the formulated problems and a weak diversity of problems were identified. Conclusions: Problem solving and posing tasks can promote mathematical creativity and knowledge, therefore should be used more often in mathematics class, allowing the construction of solid mathematical skills and enthusiasm.