The noradrenergic locus coeruleus (LC) mediates key aspects of arousal, memory, and cognition in structured tasks, but its contribution to naturalistic behavior remains unclear. LC activity is thought to multiplex distinct signals by superimposing sustained (“tonic”) firing patterns reflecting global brain states, such as arousal and anxiety, and rapidly fluctuating (“phasic”) bursts signaling discrete behaviorally significant events. Manipulations of the LC noradrenergic system broadly impair social behavior, but the temporal structure of LC firing and its relationship to social interaction is unknown. One possibility is that tonic firing may increase in the presence of social partners; it is also possible that phasic bursts may accompany specific social events. We used chronic in vivo electrophysiology and fiber photometry to measure single-unit and population neural activity in LC of freely behaving mice during their interactions with pups. We find that pup retrieval elicits remarkably precise phasic ac...