Laboratory animal science represents a challenging and controversial form of human-animal relations because its practice involves the deliberate and inadvertent harming and killing of animals. Consequently, animal research has formed the focus of intense ethical concern and regulation within the UK, in order to minimize the suffering and pain experienced by those animals whose living bodies model human diseases amongst other things. This paper draws on longitudinal ethnographic research and in-depth interviews undertaken with junior laboratory animal technicians (ATs) in UK universities between 2013 and 2015, plus insights from interviews with key stakeholders in laboratory animal welfare. In our analysis, we examine four key dimensions of care work in laboratory animal research: (i) the specific skills and sensitivities required; (ii) the role of previous experiences of animal care; (iii) the influence of institutional and affective environments and (iv) experiences of killing. We propose that different notions of care are enacted alongside, not only permitted levels of harm inflicted on research animals following research protocols, but also harms to ATs in the processes of caring and killing animals. Concluding, we argue for greater articulation of the coexistence of care and harms across debates in geography about care and human-animal relations.