English co-teaching by a native English-speaking teacher (NE) and a non-native English-speaking teacher (NN) is a common instructional practice in many English as a Foreign Language (EFL) contexts. This paper explores how two co-teachers collaborate during teacher-fronted interactions from a micro-interactional perspective, focusing on a Korean elementary school English classroom. Five video-taped lessons were analyzed to identify the participation patterns in which teacher collaboration occurs as the non-leading teacher intervenes in the ongoing talk. Teacher collaboration is realized in following two patterns: three-party interactions between the leading teacher, the non-leading teacher, and students in which the teachers jointly manage teacher talk or the floor, and two-party interactions between the leading and the non-leading teachers in which they offer and receive help in the face of trouble or to achieve an instructional goal. The sequential analysis of these diversions from the typical teacher-student, two-party interactional structure shows how the presence of two co-teachers is made salient and utilized in the work of teaching and learning. The findings indicate that teacher collaboration is not necessarily planned but rather occurs to meet unforeseen interactional and instructional needs.