The atypical behaviour of preterm infants can elicit stress in fathers and influence their ability to perceive and interpret infants' cues. This study investigated whether fathers of moderately and late preterm infants were more stressed than fathers of term infants. In a randomised controlled trial, we also studied the effect of the Mother-Infant Transaction Program on fathers' stress at six and 12 months by using the Parenting Stress Index. Infants with gestational age greater than or equal to 30.0 and less than 36 weeks were randomised to a preterm intervention group (n = 32) or a preterm control group (n = 37). A term reference group (n = 39) was also recruited. Fathers of preterm infants reported higher "total stress" than fathers of term infants at six (p = 0.002) and 12 months (p = 0.03). No significant differences were found in stress between preterm intervention and preterm control group. The intervention failed to reduce paternal stress, and the results may indicate that fathers require different intervention strategies. (Contains 4 tables and 1 figure.)