For much of the past three decades, China has witnessed a dramatic and steady increase in internal migration and thus has a huge population of left-behind children. The impact of childhood left-behind experiences has been carefully studied, but research on the long-term effects of these experiences is generally lacking. Capitalizing on a study of migrant workers conducted in Yangtze River Delta and Pearl River Delta regions, we extend this line of research by examining how childhood experiences of being left behind by migrant parents affect the behaviors of adults. Our study shows that people with left-behind experiences (1) are more likely to work overtime, which could result from avoidance of close interpersonal interaction after work; (2) spend a larger part of their income on surfing the Internet, indicating that they prefer activities not involving direct contact with other people; and (3) occurring at different stages of life can have varied long-term impacts. This study not only echoes earlier studies on the relationship between family structure and children’s behavioral outcomes, but also provides substantial evidence of the long-term negative effect of childhood left-behind experiences on adults.