Public health requires collaborations across several disciplines to meet population health needs. Increasing technological advancements have accelerated the transformation of public health to digital public health (DiPH), including new domains to develop, maintain, and improve evidence-based digital technologies. However, having various disciplines collaborating can create unique challenges if there is no mutual understanding of DiPH. This chapter aims to illustrate and discuss interdisciplinary approaches and collaborations in DiPH research and practice. First, we will give an overview of the concept of interdisciplinarity and draw on the practical challenges of interdisciplinary research and best practice examples for promoting such competencies. Second, we will describe traditional public health core functions and their relationship with other disciplines in the social, natural, and environmental sciences and humanities. Third, we will highlight how the extension to DiPH influenced the so-called system of sub-disciplines that form public health. Fourth, we will use a case study on mental health and medical apps to highlight essential strengths and limitations of selected sub-disciplines in DiPH (epidemiology, psychology, philosophy, law, computer science, and implementation science). Finally, we provide seven key recommendations that should promote and foster effective interdisciplinary collaborations in DiPH.