Teacher cognition has been a major topic of interest in applied linguistics as researchers have worked toward "better understanding the fullness of the work of teaching, a fullness that has proved complex and problematic" (Burns et al., 2015, p. 585). This qualitative study draws upon participant interview data in order to analyze and understand language teacher cognition and pedagogical knowledge development of an under-represented cohort--foreign assistant language teachers (ALTs) in Japan. Participants (n=35) were current or former ALTs with 1 to 19 years of experience working as team teachers in Japan. Interview data was transcribed and coded according to six common features of complex dynamic systems: initial condition, unpredictability, nested structure, non-hierarchic networks, feedback loops, and self-organization (Kiss, 2012). Findings show that ALTs' ability to acquire and operationalize pedagogical knowledge is highly dependent on the maneuver that they must undergo in working within the local Japanese contexts--as opposed to those in their home countries--and in relation to their colleagues who have a variety of individual traits, pedagogical beliefs, and team-teaching practices. This article serves as evidence that language teacher cognition regarding pedagogical knowledge development can be aptly understood through the lens of complex systems theory.