Background: Reading comprehension can be considered the main learning activity. All learning experiences are infused with emotions; however, to date, few studies have focused on the role of emotional aspects in reading comprehension performance. The impact of emotions on academic achievement is thought to be mediated or moderated by cognitive aspects. Among them, working memory updating is an executive function that plays a crucial role in reading comprehension. Aims: This study aimed to investigate the relationships between reading-related emotions and reading comprehension performance. We also consider the role that updating may play in these relationships. Sample: Two hundred and eight 8th graders were involved in four sessions. Method: Students completed measures of achievement emotions specifically related to reading comprehension activity, updating, and reading comprehension performance. Gender and general cognitive ability were also considered as control variables. Mixed-effects models were used for statistical analyses. According to the Akaike information criterion (AIC; Akaike, 1974), we selected the most plausible model among a set of candidate models fitted to the same data. Results: Results showed that activating-negative emotions (i.e., anxiety, anger, and shame), deactivating-negative emotions (i.e., boredom and hopelessness), and updating are related with reading comprehension performance. Moreover, the interaction between activating-negative emotions and updating also emerged. When activating-negative emotions interact with low and moderate updating, students' reading comprehension performance gets worse. Conclusions: The study indicates the moderating role of a main cognitive ability in the link between reading-related emotions and reading comprehension performance. Strategies can be taught to improve students' ability to self-regulate negative emotions and to update information in working memory.