The topic of informal learning and work has quickly become a staple in contemporary work and adult learning research internationally. The narrow conceptualization of work is briefly challenged before the article turns to a review of the historical origins as well as contemporary theories and methods involved in researching informal learning and work. I review leading theoretical models by Livingstone, Eraut and Illeris, and summarize established methods in terms of case study, ethnographic and interview approaches, survey approaches and situated micro-analytic approaches. I argue that no single theoretical model or methodological approach has yet established dominance, and that these models and methods largely speak to distinctive, not wholly incompatible, features of the phenomena in question. I argue this suggests the potential for cross-fertilization of ideas is high. (Contains 3 figures.)