Excessive monitoring of one's performance is a characteristic of anxiety disorders that has been linked to alterations in implicit emotion regulation (ER), including elevations in neural measures of performance monitoring (i.e., error- and correct-related negativity; ERN and CRN). Elevations in ERN and CRN amplitudes have been reported consistently in anxiety disorders, suggesting that an overactive performance monitoring system is linked to ER difficulties in anxiety. Yet, the relevance of these lab-based neural measures for day-to-day emotional functioning remains poorly understood. This study examined the degree to which ERN and CRN amplitudes are associated with measures of daily ER difficulties in youth with anxiety disorders. Youth (N = 100, Mage = 11.14, SDage = 1.46) completed a computerized flanker task assessing the ERN and CRN. They then completed a 5-day ecological momentary assessment (EMA) protocol assessing their daily ER (i.e., intensity of momentary and peak negative affect, intensity of worry, reliance on maladaptive ER strategies). Results showed that more negative mean CRN amplitudes were associated with higher levels of negative emotional reactivity and more intense worries. There were no significant associations between ERN amplitude and EMA measures. Furthermore, elevations in CRN were linked to more frequent use of maladaptive ER strategies (i.e., rumination, physiological reactivity, avoidance). Together, results indicate that among youth with anxiety, individual differences in CRN, but not ERN, amplitudes are related to daily ER difficulties. Findings highlight the clinical utility of a lab-based neural measure of ER, suggesting that the CRN, rather than the ERN, reflects individual ER differences in the context of daily life among youth with pediatric anxiety disorders. As such, the CRN might serve as an important dimensional index of a treatment target that can be tracked with a validated, multi-method measure.