Metacognition (MC) and executive functions (EF) have traditionally been investigated separately although these two constructs share commonalities and show a similar developmental timeline (Marulis et al. 2020; Roebers 2017). Despite recent theoretical attempts to bring them together under a unifying framework (e.g. Roebers, 2017), especially on the monitoring aspect, there is still very limited empirical evidence. Moreover, the existing studies have revealed mixed findings. One study found that 3- to 5-year-old children’s EF was positively predicted by their MC, even after controlling for age and language skills (Marulis & Nelson, 2021). Similarly, Bryce et al. (2015) found EF to be related to MC, more so in 5 years of age than 7 years of age and suggested that EF might be a necessary but not sufficient constituent of MC. Another study found no longitudinal prediction from an 8 year-old's EF to their MC 8 months later (Spiess et al., 2016). Roebers et al. (2012) found that 7-8 year-olds’s EF was concurrently related to their MC control but not monitoring, and EF at 7 years longitudinally predicted MC control at 8 years. A growing body of evidence suggests a differentiation between explicit and implicit metacognition and that children as young as 2.5 years of age show signs of implicit metacognition (Geurten & Bastin, 2018; Kälin & Roebers, 2020; Paulus et al., 2013). Previous research examining the associations between EF and MC has mainly focused on explicit MC, yet this distinction may be important to take into account. For instance, a recent study found that 4-6 year-old children’s EF was associated with their latency of confidence judgments (CJ), which reflects implicit metacognitive monitoring, but not with their explicit CJ, which reflects explicit metacognitive monitoring (Kälin & Roebers, 2020). Moreover, different patterns were revealed for the different EF components. More specifically, inhibition accuracy was positively related to latency of confidence judgments for correct and incorrect answers. Shifting accuracy was positively related and shifting reaction time (RT) was negatively related to latency of CJ for correct answers. Inhibition RT and working memory accuracy were not significantly related to any MC measure. Another important aspect to consider is that the previous research examining this link between EF and MC exclusively used average accuracy and/or RT measures of EF. However, especially considering the hypothesis that the monitoring component could underlie the link between EF and MC, using measures more exactly tapping this monitoring component is essential. The monitoring aspect in EF is best captured by trial-by-trial measures such as post-error slowing (PES). Hence, we aim to explore the associations between not only the traditional accuracy and RT measures of EF, on the one side, but also post-error slowing in EF, on the other side, and both implicit and explicit measures of metacognitive monitoring judgments. There seems to be a developmental shift between the ages of 5 to 7 where the association between MC and EF gets weaker (Bryce et al., 2015), narrowed down to control (Roebers et al., 2012), or reverse direction (Marulis & Nelson, 2021 vs. Roebers et al., 2012). Hence examining this age period might give the most insight into the relationship between MC and EF. In this study, we examine this age period in two groups that differ in their grade in the Swiss education system: Kindergartners (5-6 year-olds) and 1st graders (6-7 year-olds), which allows us to confirm any pattern of relationship in two adjacent age groups. Given that previous studies, even those finding relations of EF only to MC control but not monitoring (Roebers et al., 2012), did not use trial-by-trial measures of EF, which captures the monitoring in EF better, which is a more implicit measure than average accuracy and RT. We argue that this implicit EF component would be associated with an implicit measure of MC monitoring and the more explicit accuracy and RT measures from the EF task would be associated with an explicit measure of MC monitoring.