We apply a biopsychosocial conceptualization to attention development in the 1st year and examine the role of neurophysiological and social processes on the development of early attention processes. We tested whether maternal behavior measured during 2 mother-child interaction tasks when infants (N = 388) were 5 months predicted infant medial frontal (F3/F4) EEG power and observed attention behavior during an attention task at 10 months. After controlling for infant attention behavior and EEG power in the same task measured at an earlier 5-month time point, results indicated a significant direct and positive association from 5-month maternal positive affect to infant attention behavior at 10 months. However, maternal positive affect was not related to medial frontal EEG power. In contrast, 5-month maternal intrusive behavior was associated with infants' task-related EEG power change at the left frontal location, F3, at 10 months of age. The test of indirect effects from 5-month maternal intrusiveness to 10-month infant attention behavior via infants' EEG power change at F3 was significant. These findings suggest that the development of neural networks serving attention processes may be 1 mechanism through which early maternal behavior is related to infant attention development in the 1st year and that intrusive maternal behavior may have a particularly disruptive effect on this process.