Background Allied health comprises multiple professional groups including dietetics, medical radiation practitioners, occupational therapists, optometrists and psychologists. Different to medical and nursing, Allied health are often organized in discipline specific departments and allocate budgets within these to provide services to a range of clinical areas. Little is known of how managers of allied health go about allocating these resources, the factors they consider when making these decisions, and the sources of information they rely upon. The purpose of this study was to identify the key factors that allied health consider when making resource allocation decisions and the sources of information they are based upon. Methods Four forums were conducted each consisting of case studies, a large group discussion and two hypothetical scenarios to elicit data. A thematic content analysis commenced during post-forum discussions of key factors by forum facilitators. These factors were then presented to an expert working party for further discussion and refinement. Transcripts were generated of all data recordings and a detailed thematic analysis was undertaken by one author to ensure coded data matched the initial thematic analysis. Results Twelve factors affecting the decision-making of allied health managers and clinicians were identified. One of these factors was disendorsed by the expert working party. The ۱۱ remaining factors can be considered to be key decision-making principles that should be consistently applied to resource allocation. These principles were clustered into three overarching themes of readiness, impact and appropriateness. Conclusion Understanding these principles now means further research can be completed to more effectively integrate research evidence into health policy and service delivery, create partnerships among policy-makers, managers, service providers and researchers, and to provide support to answer difficult questions that policy-makers, managers and service providers face.