The present study examined frontal electroencephalography (EEG) asymmetry and negative affectivity (NA) as predictors of infant behaviors during the Still-Face Paradigm (SFP). It was hypothesized that infants with lower NA subscale scores who also demonstrate greater left frontal activation would exhibit more frequent social engagement and self-soothing behaviors during the SFP. Mothers reported infant temperament at 6–12 months of age (N = 62), and EEG was recorded during a baseline task and the SFP. Social engagement, distress, and self-soothing behaviors were coded during the SFP. A three-factor solution emerged based on exploratory factor analysis of eight infant behaviors. After considering bivariate relations, multiple regression analyses predicting the behavior factor labeled social engagement (containing vocalizations and handwaving; average factor loading = .56) were conducted separately for asymmetry and NA subscales, controlling for infant sex and age. The SFP asymmetry predicted social engagement after controlling for covariates and baseline asymmetry; however, NA subscales (falling reactivity and distress to limitations) did not uniquely explain significant variance. These findings highlight the importance of frontal EEG asymmetry in contributing to emerging social engagement and regulation in infancy. Implications include potentially utilizing asymmetry markers as screening and intervention targets in the first year of life.