Abstract Facial expressions are fundamental to social communication, with emotional face processing developing throughout childhood. However, the neural mechanisms underlying this process in young children remain underexplored due to challenges in neuroimaging this population. Optically pumped magnetometers (OPMs), a wearable magnetoencephalography (MEG) technology, offer potential advantages for studying these responses early in life. This study investigated evoked responses and functional connectivity in 45 children (3–5 years) during an emotional face processing task using OPM-MEG. The M170 component, a key marker of face processing, and whole-brain functional connectivity of eight regions of interest were assessed. Children exhibited a robust M170 response to emotional faces in the bilateral fusiform gyri. Peak amplitude increased with age, but no significant latency changes were observed. A significant network of increased connectivity following emotional face onset, involving connections between the amygdalae, insulae, occipital, and frontal regions was found. This study provides the first evidence of M170 responses and large-scale connectivity to emotional faces in young children using OPM-MEG. Findings highlight the feasibility of OPMs for developmental neuroimaging and provide insights into the maturation of emotion-related neural circuits in early childhood. These results establish a foundation for future face processing research in clinical paediatric populations, such as autism.