This study investigated the influence of the intervention process on the effectiveness of a program aimed at promoting positive parenting. The study involved a homogeneous intervention sample (N = 120) of mothers and their 1-, 2-, or 3-year-old children screened for high levels of externalizing problems. The alliance between mother and intervener, mothers' active skills implementation, and father involvement were examined in relation to changes in maternal sensitivity and positive discipline strategies. Results revealed that only alliance predicted change in positive parenting. Implications for future process evaluations and intervention programs are discussed. © 2008 Wiley Periodicals, Inc.