This article contributes to research perspectives on the topic of proactive self-tracking. Self-tracking, referring to the employment of near-body biometric technologies such as activity wristbands and sleep tracking devices that collect data on bodies, is a popular practice of health-related life management, and thus an object of interest across a variety of research fields. However, we argue that much of the research throughout the various fields subscribes, to some degree, to a bifurcating ‘ontology of being’ through which the human and the technical are separated from each other at the level of ontological presumptions. In this article, we draw from a range of (new) materialist philosophy and discussions in the field of science and technology studies, and propose a shift towards a processual ‘ontology of becoming’ in self-tracking research. We suggest some theoretical and conceptual fine-tunings through which research may be better equipped to investigate the processuality of actors and multidirectional flows of agency in self-tracking practices. While our main contribution is theoretical, we will also illustratively analyze two interview narratives of self-tracking in order to demonstrate the different types of research worlds that open up depending on the ontological perspective taken.