This study reports on the incorporation of mobile instant messaging (MIM) in assessments, as a collaborative learning tool, to enable students to socially construct knowledge and develop their collaborative problem solving competence, while being assessed individually. In particular, this study explores: what is the extent and timing of students' use of MIM to communicate with other students while being assessed individually? What communicative activities are evident in the content of students' MIM communications while being assessed individually? How do students experience being able to use MIM while being assessed individually? The results of this study's analysis of the messages sent during various assessments suggests that when incorporating MIM into assessments, instructors should consider the objective of those assessments together with the nature (e.g. essay style) and the stakes of the assessments as these appear to influence the extent, timing and content of the instant messaging communications by the students during the assessment. A survey of the students suggested that their experiences of being able to use MIM during assessments were largely positive due to the learning opportunities, collaboration and teamwork, authenticity and equity that the introduction of instant messaging during assessment enabled.