This study evaluated the effectiveness of the Triple P (Primary Care and/or Group) parenting support program on various aspects of the parenting experience through a quasi-experimental pretest – post-test protocol with an active comparison group (Care as usual). A sample of 384 parents assigned to two groups (n Triple P = 291; n Care as usual = 93) completed three subscales of the Parenting Stress Index – 4 – Short Form (Parental Distress, Parent-Child Dysfunctional Interaction, and Difficult Child) and the Parental Self-Agency Measure. The amount of intervention received by each parent was considered in the analyses. Path analysis showed that the type (Triple P vs Care as usual) and the amount of intervention (number of sessions attended) contributed independently to predicting changes in parenting experience between pretest and post-test. Receiving Triple P was systematically associated with more positive outcomes than receiving care as usual, whereas more intervention was positively associated with improved self-efficacy and parent-child relationship quality. Overall, the model explained between 4.0% and 12.6% of the variance in individual change, depending on the outcome, suggesting that unmeasured drivers of change came into play. A follow-up of parents in the Triple P group two to four years after the end of the program (n follow-up = 164) showed that the observed changes were maintained over time, with moderate to large effect sizes. These results help to broaden the evidence base on the effectiveness of this program in a sociocultural and linguistic context different from that in which it was developed.