The aim of this article is to assess the effects on learners' emotions and emotion regulation of an intervention promoting the development of cognitive strategies for mathematical problem-solving and positive perceptions of problem-solving competence (SEP), embedded in an overall self-regulated approach, with upper elementary students (N = 334, mean age = 10.6 years). Using a quantitative quasi-experimental design (three measurement points), two conditions (cognition vs. cognition + SEP) were contrasted with a control group. Findings revealed that the combined condition stood out positively from the other two in terms of level of SEP, indicating that the SEP-related part of the designed intervention did effectively support the learners' SEP. With regard to effects on emotions and emotion regulation, although nurturing one dimension (cognition) produced beneficial effects, fostering two dimensions (cognition + SEP) led to more and stronger benefits in terms of both emotions and emotion regulation strategies. Participants in both experimental conditions also substantially improved their problem-solving performance. The implications in terms of pedagogical practices for teachers are also discussed.