BACKGROUND: Parental bonding towards the child holds substantial importance in child development and the mental well-being of parents and children alike. Therefore, it is crucial to gain insights into the diverse trajectories that bonding difficulties may follow during the postpartum period. This study addresses a research gap by exploring the trajectories of both maternal and paternal bonding difficulties with the inclusion of various potential predictor variables of trajectory class membership in a large community-based sample. METHODS: This study utilized data from the longitudinal cohort study DREAM to investigate the trajectories of maternal (n = 1,761) and paternal (n = 1,128) bonding difficulties at eight weeks, 14 months, and two years postpartum. To identify distinct trajectories of bonding difficulties, Growth Mixture Modeling was employed. Additionally, several potential predictors of trajectory class membership were examined through multinomial logistic regression, including parental mental health factors, subjective birth experience, difficult child temperament, interpersonal factors, and sociodemographic characteristics. RESULTS: Three distinct bonding difficulty trajectory classes emerged in both maternal and paternal samples: "low-steady" (persistently low difficulties), "recovering" (initially high but decreasing difficulties), and "aggravating" (clinically significant and increasing difficulties). Parents in the "recovering" and "aggravating" classes not only encountered clinically significant bonding difficulties at some point during the study period, but also experienced fluctuating bonding difficulties over time. Multinomial logistic regression analysis also revealed various predictors of trajectory class membership. For mothers, significant predictors included anger/hostility symptoms, subjective birth experience, and difficult child temperament. For fathers, predictors included subjective birth experience, difficult child temperament, first-time parenthood, and age. CONCLUSION: This study challenges the notion of bonding as a stable phenomenon through the identification of non-steady trajectories, acknowledging the importance of recognizing that clinical bonding difficulties tend to manifest in non-steady courses over time. Recognizing these diverse trajectories of bonding difficulties and their predictors offers valuable insights for the development of more effective interventions and support systems to promote healthy parent-child bonding.