The aim of this study was to examine whether professional collaboration in home health care is associated with clear boundaries between principals' areas of responsibility and the professions areas of responsibility, respectively. Data were derived from a web-based survey that was carried out in one county in the middle of Sweden during spring 2013. Participants were health professionals and managers from the county council and from all the municipalities in the county. Both structured and open-ended questions were utilised. A total of 421 individuals (90% women) answered the structured questions, and 91 individuals (22% of the 421) answered the open-ended questions. Quantitative data were analysed with descriptive statistics methods, tests of independence and of correlation strength. Qualitative data were analysed with content analysis. The results from the structured questions showed that well-functioning collaboration was associated with clear boundaries between principals in the county overall, and for respondents in two of three parts of the county. Association between clear boundaries between professions and well-functioning collaboration was found in the county overall among the municipality population. However, in one part of the county, we did not find any correlations between well-functioning collaboration and clear boundaries between professions or principals, with the exception of home help services. The analysis of the open questions gave similar results as the quantitative analysis, illustrated within three themes: The significance of concepts, trust and interdependence, and collaboration as a means for well-being. The results indicate that, recently after an organisational change, clear boundaries between the principals' areas of responsibility and professions' area of responsibility respectively are necessary for effective cooperation between professionals. If the organisation and professionals have previous positive experience of colocated activities, clear boundaries do not share the same importance.