<p>Metacognitive regulation, which encompasses both monitoring and control processes, is thought to be of great importance to learning and academic success. Despite its importance, most research focuses on metacognitive monitoring, excluding metacognitive control. Moreover, its developmental trajectory, particularly in the context of arithmetic, remains underexplored. This study examined the development of metacognitive regulation in arithmetic. We performed a cross-sectional investigation in 7-8-year-olds (<i>n</i> = 114), 10-11-year-olds (<i>n</i> = 102), adolescents (<i>n</i> = 99), and adults (<i>n</i> = 102). Participants completed two arithmetic tasks. In one task we measured post-error slowing (PES) as an indicator of metacognitive control. In the other task, we used retrospective confidence judgments as an indicator of metacognitive monitoring. Results demonstrate that people slow down after committing an error across all age groups, with the magnitude of PES decreasing with age. Although the ability to monitor one’s performance initially appeared to improve with age, this effect disappeared when task performance was controlled for. Notably, monitoring correlated with arithmetic performance across all age groups, while PES showed only associations with task performance and metacognitive monitoring in 7-8-year-olds and not in older age groups. These results indicate that although individuals slow down after making errors, the limited effectiveness of this strategy in improving performance appears to diminish with age. People might apply other, perhaps proactive, control strategies, as they get older. These results deepen our understanding of the development of metacognitive regulation in relation to academic performance and can inform strategies to effectively support children’s learning and academic success.</p>