This paper explores the similarities and differences between complexity science's and cultural-historical activity theory's understandings of human learning. Notable similarities include their emphasis on the importance of social systems or collectives in understanding human knowledge and practices, as well as their characterization of systems' internal dynamics and transformations. The most important difference is that cultural-historical activity theory views activity systems and the dialectical relationship between persons and societal wholes as the central and determining factor with regard to human learning and knowledge, whereas complexity science asserts that there are other relationships and systems that are directly relevant to human knowing as well.