Over the last three decades there has been a rise in the number of workers employed during nonstandard (evening and overnight) hours; accompanying this trend has been a renewed interest in documenting the well-being of these workers and their families. However, no work has considered how participation in nonparental child care during nonstandard hours is associated with child development That is the aim of the current paper. Using repeated cross-sectional data from the 1999 and 2002 National Survey of America's Families (NSAF), this paper investigates the relationship between participation in nonstandard hours of nonparental child care ('nonstandard child care') and child well-being. I begin this investigation by classifying children as participants or nonparticipants in nonstandard child care; next, I specify a child production function to estimate the relationship between nonstandard child care and child well-being. I find a generally negative relationship between nonstandard child care and cognitive, behavioral, and contemporaneous physical well-being measures. Mechanisms analyses suggest this relationship is driven by exposure to low-quality, unpredictable care arrangements. (author abstract)