Objective: Becoming a mother is a process of transition that is subject to constant change and may last for over one year postpartum. Bonding is an important component of this transition to motherhood and can be measured with the Postpartum Bonding Questionnaire (PBQ). Most often, the PBQ is used among mothers up to 12 weeks postpartum. However, the transition to motherhood – and thus bonding – takes much longer and usually continues until 12 months postpartum.Design: Validation study to test the PBQ for validity and reliability for use among mothers up to one year postpartum. Internal consistency and construct validity were established using Cronbach’s Alpha,exploratory factor analysis (EFA) and subsequent confirmatory factor analysis (CFA).Setting: mothers living in Flanders, Belgium.Participants: The sample was composed of 254 Flemish mothers who had given birth to healthy neonates up to one year earlier.Findings: The EFA (principal component analysis) resulted in a uni-dimensional factor, “Impaired Bonding”, consisting of 21 items. Four items were excluded because of a low factor load. This uni-dimensional version of the PBQ was checked with CFA, resulting in an acceptable model-of-fit: significant X2 (p < 0.001), CMIN/df = 2.61, CFI = 0.85, RMSEA = 0.08. The internal consistency of the 21-item version showed a Cronbach’s alpha of 0.89.Key conclusion: The 21-item version of the PBQ is a valid and reliable tool to identify bonding in a general population of Flemish mothers up to one year postpartum. Further research is of merit.