The attachment representation (AR) of individuals affects emotional and cognitive information processes and is considered an important modulating factor of neuroendocrine stress responses. The neuropeptide oxytocin is studied as one biomolecular component underpinning this modulation. A validated procedure used in attachment-related research is the Adult Attachment Projective Picture System (AAP). To date, only a limited number of studies investigated oxytocin and neuroendocrine reactivity in the context of an attachment-related stimulus similar to the APP. In this pilot study, N = 26 men of recent fatherhood were exposed to the AAP to classify AR and to investigate salivary changes in oxytocin, cortisol and dehydroepiandrosterone (DHEA) after AAP stimulation. We observed increased oxytocin levels in response to AAP exposure, and this increase was more pronounced in fathers with unresolved/disorganized AR. No significant changes in cortisol and DHEA concentrations were observed in response to AAP administration. Interestingly, differences in basal cortisol levels (before the AAP) also depended on AR classification. Here, the group of men with unresolved/disorganized AR showed higher levels of cortisol compared to fathers with organized AR. To conclude, the finding of increased salivary oxytocin levels in response to the AAP further indicates its validity as an instrument to stimulate the attachment system.