Activity theory, except for a few publications in western journals, remained unknown outside the Soviet Union until the mid-1980s, when it was picked up by Scandinavian researchers. (The first international conference on activity theory was not held until 1986. The earliest non-Soviet paper cited by Nardi is a 1987 paper by Yrjö Engeström : "Learning by expanding"). This resulted in a reformulation of activity theory. Kuutti notes that the term activity theory "can be used in two senses: referring to the original Soviet tradition... or referring to the international, multi-voiced community applying the original ideas and developing them further."

Some of the changes are a systematisation of Leontiev's work. Although Leontiev's exposition is clear and well structured, it is not as well-structured as the formulation by Yrjö Engeström. Kaptelinin remarks that Engestrøm "proposed a scheme of activity different from that by [Leontiev]; it contains three interacting entities—the individual, the object and the community—instead of the two components—the individual and the object—in [Leontiev]'s original scheme."