This study examines the influence of parental anxiety on stress regulation in children aged 6 to 10 years, a developmental period that is critical for socio-emotional maturation. Grounded in affective neuroscience and developmental psychology, it is hypothesized that chronic parental anxiety may compromise the buffering effect typically afforded by parental presence during stress, by disrupting mechanisms of emotional co-regulation. Twenty parent–child dyads were exposed to a moderate stress paradigm (adapted MIST) under two conditions: the presence of the parent or the presence of an unfamiliar adult. A multimodal assessment was employed, integrating physiological indices (cortisol, alpha-amylase), subjective measures (emotional rating scales), and neural data (resting-state fMRI). Results indicate that parental presence can serve as a social buffer, particularly in older children. However, the moderating effect of parental anxiety on physiological and neural responses was not clearly demonstrated. Preliminary trends suggest a subtle influence of parental anxiety, warranting further investigation. These findings underscore the complexity of co-regulatory processes in the context of childhood stress.