The professionalisation of doula care and research interest in this area of maternity care/support have both grown internationally in recent years highlighting important broader issues around the access, continuity and delivery of maternity care services. However, no work to date has provided a critical appraisal of the international literature on this topic. In response, this paper presents the first critical review of international empirical literature examining professional doula care for pregnant and birthing women. A database search of AMED, CINAHL, Maternity and Infant Care, and MEDLINE using the search term, “doula” was undertaken. A total of 48 papers published between 1980 and March 2013 involving trained or professional doulas were extracted. Four descriptive categories were identified from the review: ‘workforce and professional issues in doula care’; ‘trained or professional doula's role and skill’; ‘physical outcomes of trained or professional doula care’; and ‘social outcomes of trained or professional doula care’. Of the studies evaluating outcomes of doula care, there were a number with design and methodology weaknesses. The review highlights a number of gaps in the research literature including a lack of research examining doula workforce issues; focus upon the experience and perspective of significant stakeholders such as expectant fathers with regard to trained or professional doula care; clinical trials measuring both subjective experiences and physical outcomes of trained or professional doula support; synergy between the design of clinical trials research examining trained or professional doula care and the clinical reality of professional doula practice. It is imperative that key aspects of trained doula care be subject to further rigorous, empirical investigation to help establish an evidence base to guide policy and practice relating to this area of support and care for pregnant and birthing women.