Aim/Purpose: The purpose of this study was to analyze the online teacher-students' interactions using WhatsApp, an instant messaging tool, and to identify the students' view towards the use of that tool in a law course from a higher education institution in Colombia. Background: WhatsApp is a trending tool that is ultimately being used in academic contexts. However, little research is known on the types of interactions that occur when teachers are involved in student conversation groups. Methodology: This is a mixed-method study. Participants completed an opinion survey in order to establish students' satisfaction towards the use of WhatsApp to complement face-to-face classes, a focus group to explore in depth the students' opinions and acceptance of the WhatsApp tool for academic purposes and a chat conversation register to analyze the different types of interactions. The sample included 166 Law students. Contribution: Our contribution is to enrich the current literature on the interactions between teachers and students in a virtual environment where teachers can monitor the different academic tasks, coordinate in real time and analyze the students' interactions that impact on the students' learning process. Findings: The findings found in this research reveal that the different interactions between students and teachers in order to facilitate learning should be valued not only the relationships of knowledge construction, but also the social and interdependence presences due to the fact that in traditional learning processes they are not usually taken into account. Recommendations for Practitioners: The results of our research give evidence of how students in each subgroup (Plaintiffs, Defendant or Judges) diversify the use of the WhatsApp tool. Whether it is to organize, coordinate meetings, plan work, make quick inquiries, clear doubts, share messages and especially be able to communicate in real time and directly with the teacher, thus facilitating the learning process in the classroom. Recommendation for Researchers: This study identified that law university students appear to have a special preference for the WhatsApp tool, thanks to the immediacy of being able to coordinate tasks and communicate with the teacher, in comparison to using other technological means such as email. We recommend continuing to explore the use of WhatsApp in other different disciplines in order to compare the teacher student interactions. Impact on Society: The analysis of academic interactions through WhatsApp may lead to further exploration of innovative forms of communication of teachers with their millennial students and new teacher roles to design constructive learning environments. Future Research: Future studies are suggested with regard to this topic and it would be interesting to carry out research work that deeply analyzes the role the instructor plays when participating in a WhatsApp chat group with academic purposes and how it may condition the way students interact.