In this paper we maintain that 21st century science is, fundamentally, a relational process in which knowledge is produced (or co-produced) through transactions among researchers or among researchers and public stakeholders. We offer an expanded perspective on the practice of 21st century science, the production of scientific knowledge, and what community psychology can contribute to these developments. We argue that: 1) trends in science show that research is increasingly being conducted in teams; 2) scientific teams, such as transdisciplinary teams of researchers or of researchers collaborating with various public stakeholders, are better able to address complex challenges; 3) transdisciplinary scientific teams are part of the larger, 21st century transformation in science; 4) the concept of heterarchy is a heuristic for team science aligned with this transformation; 5) a contemporary philosophy of science known as perspectivism provides an essential foundation to advance 21st century science; and 6) community psychology, through its core principles and practice competencies, offers theoretical and practical expertise for advancing team science and the transformation in science currently underway. We discuss the implications of these points and illustrate them briefly with two examples of transdisciplinary team science from our own work. We conclude that a new narrative is emerging for science in the 21st century that draws on interpersonal transactions in teams, and active engagement by researchers with the public to address critical accountabilities. Because of its core organizing principles and unique blend of expertise on the intersection of research and practice, community psychologists are extraordinarily well-prepared to help advance these developments, and thus have much to offer 21st century science.