BackgroundParenting of preterm infants presents unique challenges, particularly during their transition from hospital to home. Early discharge programs can assist parents during this critical period. However, the feasibility of delivering a family-focused online discharge program remains understudied. ObjectivesThis study was conducted to investigate the impact of a family-focused online parenting support intervention on parents' sense of competence, depression, caregiving, social support, family functioning, and the weight and length of preterm infants. MethodsWe conducted a single-blind, two-arm randomized controlled trial with a repeated-measures design. Participants were recruited from a specialized tertiary hospital in China between May and December 2022. Forty-five families were randomly assigned to the intervention group and 44 to the control group. The intervention included three components: (1) two one-hour group sessions and three 30-minute individual sessions of online parenting support; (2) two follow-up telephone calls (15–30 min each) post-discharge; and (3) access to online parenting resources. Primary outcomes included parenting sense of competence, parental care ability, and preterm infants' weight and length. Secondary outcomes included depression, social support, and family functioning. Measurements were taken at baseline, preterm infant discharge, one month post-discharge, and three months post-discharge. A generalized estimating equation model was employed based on the intention-to-treat principle for outcome comparison. ResultsParents in the intervention group showed significant improvements in parenting sense of competence (P < 0.001), parental care ability (P < 0.001), depression (P < 0.001), and social support (P = 0.002). However, no statistically significant differences were observed in preterm infants' weight and length, or in family functioning (P > 0.05). ConclusionsAlthough the intervention did not affect preterm infants' outcomes, the positive enhancements in parenting sense of competence, care ability, depression, and social support indicate that online family-focused parenting support can effectively prepare parents for hospital discharge and the early transition period.