Three issues were investigated: (a) the regulatory effects of presumed infant and maternal regulation behaviors on infant distress to novelty at 6 months, (b) stability of infant regulatory effects across contexts that vary in maternal involvement, and (c) associations and temporal dynamics between infant and maternal regulation behaviors. Participants were 87 low-risk infants and their mothers, observed at 6 months postpartum during infant exposure to novel toys. Contingencies derived from sequential analyses demonstrate that, by 6 months, some infants reduce their own distress to novelty by looking away from the novel toy or self-soothing, maternal engagement and support have comparable effects, and certain infant and maternal behaviors co-occur. Moreover, infants whose mothers engaged contingently when they looked away from the novel toy expressed less distress than comparable infants whose mothers did not. These findings implicate both infants and mothers in the development of emotion regulation during the infant's first year.