Perinatal mental health disorders potentially have long-term negative sequelae for women, their infants and their families. Multidisciplinary perinatal and infant mental health (PIMH) services are an emerging specialty in mental health designed to improve mother-infant outcomes. This mixed methods study explored the characteristics of women referred to a specialist PIMH service and the therapeutic interventions that PIMH clinicians use. Women referred to the service were identified with multiple and complex risk factors. Perinatal and infant mental health clinicians use a range of interventions, dependent upon their training, such as family of origin work/genograms, non-directive counseling, and strategies to manage anxiety and depression. Clinicians also emphasized the therapeutic relationship and the interventions they use within an attachment-based framework, which warrants further research.