From a sociocultural perspective the concept of self-regulation is associated to voluntary control over higher and culturally organized mental functions such as, for example, focusing attention, planning a course of action, solving a problem, or deliberately remembering something. Thus, the ability to self-regulate is highly related to school success. The present article examines the ways by which two newly arrived immigrant Korean students, learning English as a second language while enrolled in a middle school in the United States, made use of old and new systems of signs (i.e., native and target languages) to (re)gain and maintain self-regulation in a new cultural and linguistic context. We conducted a microgenetic analysis of student-teacher and student-student interactions during two specific classroom writing practices that occurred regularly in the classroom. We found that the development (or activation) of self-regulation for the students was tightly intertwined with social and cultural contextual factors of the English-dominant classroom environment, which in turn afforded or constrained the use and acquisition of newly formed semiotic resources (e.g., hybrid sign systems) for the creation and expression of meaning. (Contains 1 footnote.)