This article reports a multiple case study in which we analyse Brazilian and Spanish mathematics teachers' opinions about and predispositions toward gamified activities in STEAM education. To obtain data, we administered a survey to 56 in-service mathematics teachers in primary and secondary education from these countries. The survey had been previously validated throughout an expert judgement process. Our results show a high percentage of teachers who think this kind of activity has positive effects on students' development, improving their affective domain toward mathematics and required skills for mathematical competency. Notwithstanding, many teachers report insecurity and lack of training for employing such educational methodologies.