Guided by Belsky's and Eisenberg, Cumberland, and Spinrad's heuristic models, we tested a process model with hypothesized paths from parents' effortful control (EC) and family chaos to indices of parenting to children's EC, and finally children's externalizing problem behavior. Parents reported on all constructs and children (N = 188; M age = 9.55 years) reported on their EC and externalizing problem behaviors. Consistent with expectations, parents' EC promoted their positive (and inhibited negative) reactions to children's negative emotions. In addition, high levels of family chaos predicted low levels of parental positive reactions to children's emotion. Children's EC was predicted by high levels of positive reactions and low levels of negative reactions. As expected, children's externalizing problem behaviors were negatively related to their EC. Results clarify possible family processes by which children's EC is enhanced and problem behaviors are reduced.