The aim of this article is to identify the main stakeholders of institutions of professional higher education in the field of internal security in selected countries, and the most important collaboration practices, and the factors that affect collaboration. Within the framework of a qualitative phenomenographic study, interviews were conducted with representatives of Estonian, German, Finnish, and Norwegian institutions of professional education in the field of internal security. The results showed that institutions of professional higher education differ from traditional universities in prioritizing their main stakeholders, putting employers first, and not students. In addition, the ministries under whose government they operate, and other higher education institutions were named as the main stakeholders. Collaboration with stakeholders is mostly based on common interests and personal relationships (e.g., mediation, networking, joint reputation building, collaboration councils), on some kind of formal basis (e.g., feedback system, collaboration councils) or subordination (e.g., execution of orders and instructions, trading). The aspects most influencing collaboration were considered to be the aspects related to trust and professionalism, and in particular informal collaboration was valued. The results of this study enabled the author to supplement a framework from a previous study, which originally described the theoretical collaboration of the stakeholders of an institution of higher education in the field of internal security; this was supplemented by adding the dimension of collaboration diversity.