Preterm birth has been associated with increased parenting stress in early infancy, and some reports have found this to be a risk factor for later behavioral problems. There are, however, few studies and conflicting results. Information about the fathers is scarce. Our goal was to study the effects of an early-intervention program on parenting stress after a preterm birth until 1 year corrected age. A randomized, controlled trial was conducted including infants with a birth weight <2000 g treated at the University Hospital of North Norway Trust, which serves the 2 northern-most counties in Norway, to examine the effects of a modified version of the Mother-Infant Transaction Program on parenting stress measured by the Parenting Stress Index. A term control group was also recruited. The Parenting Stress Index was administered to the mothers at 6 and 12 months' corrected age and to the fathers at 12 months' corrected age. The intervention consisted of 8 sessions shortly before discharge and 4 home visits by specially trained nurses focusing on the infant's unique characteristics, temperament, and developmental potential and the interaction between the infant and the parents. Seventy-one infants were included in the preterm intervention group, and 69 were included in the preterm control group. The preterm groups were well balanced. Seventy-four infants were included in the term control group. Compared with the preterm controls, both the mothers and fathers in the preterm intervention group reported significant lower scores in child domain, parent domain, and total stress on all occasions except the mother-reported child domain at 12 months. These differences were not related to birth weight or gestational age. The level of stress among the preterm intervention group was comparable to their term peers. Both parents in the intervention group reported consistently lower scores within the distractibility/hyperactivity, reinforces parents, competence, and attachment subscales compared with the preterm control group. There were no differences in mean summary stress scores between the mothers and fathers in the 2 preterm groups at 12 months, but the intraclass correlation coefficient was higher in the intervention group. This early-intervention program reduces parenting stress among both mothers and fathers of preterm infants to a level comparable to their term peers. We are now studying whether this will result in long-term beneficial effects.