ABSTRACT The focus of this study is on the interactions five pairs of students had in order to carry out a collaborative writing activity. The research was conducted in a language school of Goiânia, in Goiás, Brazil, with ten EFL/ESL students, in 2015. The objectives of this investigation are: a) to observe and discuss the elements that stand out during the students' interactions; and b) to investigate these learners' perceptions of the experience. This study is grounded on sociocultural theory (DONATO, 1994; HALL, 2001; VYGOTSKY, 1978) and collaborative language learning (FIGUEIREDO, 2005, 2006, 2008, 2015; OXFORD, 1997). The theoretical assumptions that guide this research consider interaction and collaboration as essential elements for language learning development. This is a qualitative case study (GODOY, 2006; TELLES, 2002), and the sources used to generate the data are questionnaires, audio recordings of the students' interactions and semi-structured interviews. The elements that stand out in this investigation are related to the potentialities of dialogic interactions, which foster scaffolding, mutual support, and the promotion of learners' autonomy. In addition, the learners highlight some positive aspects they could perceive from the experience, such as each other's help and the possibility to access more ideas; as negative aspects, they point out disagreements and conflicts they had to handle during the interactions.