Background <p>Preterm birth is a significant public health issue which has a substantial effect upon postpartum mental health. The implementation of kangaroo care (KC) can have positive effects for both infants and birthing parents. Yet optimal scheduling methods for KC are not yet confirmed and current recommendations may be impractical, and thus not sustainable in this context. This study aimed to evaluate the effectiveness of delivering two different scheduling methods of KC upon the mood (depressed mood) and mental health of birthing parents with preterm infants discharged from the neonatal intensive care unit (NICU).</p> Methods <p>A single-blind, randomized, clinical trial with three parallel groups (two intervention and one control) was conducted. The study samples were birthing parent– preterm infant pairs who were discharged from the NICU. Continuous sampling was conducted using six blocks, with 65 pairs allocated to each of the three groups: the scheduled KC group (KC three times daily for a minimum of 30&#xa0;min per session), the unscheduled KC group (KC as often as desired during the day for a minimum of 30&#xa0;min per session), and the control group. The intervention spanned four weeks and was executed exclusively in the home setting. The Profile of Mood States Questionnaire (POMS) (depressed mood) and the General Health Questionnaire (GHQ-28) were completed by participants pre and post intervention.</p> Results <p>Post intervention, the mean score of participants’ depressed mood as well as the total score and subscale of GHQ-28 in the two intervention groups was statistically and significantly lower than scores in the control group (<i>P</i> &lt; 0.05). There was no statistically significant difference identified between the two intervention groups.</p> Conclusion <p>This is the first study of its kind to compare the effectiveness of two different KC methods delivered to preterm infants. This study was also unique in terms of its time comparisons. Both scheduled and unscheduled KC can be used to improve the mental health of birthing parents with preterm infants. Yet as there is no statistically significant difference in terms of their effectiveness, the promotion of unscheduled KC may be more practical and thus more sustainable in this context.</p> Trial registration <p>Iranian Registry of Clinical Trials (IRCT)</p> <p>URL <a href="https://irct.behdasht.gov.ir/trial/61164">https://irct.behdasht.gov.ir/trial/61164</a></p> <p>Trial ID IRCT20090810002324N19</p> <p>Date of first registration 10/05/2022</p>