In this study, we examined a mathematics teacher's communicative acts on an instant messaging tool, WhatsApp, and its role in creating a sustained learning environment between secondary-school students and a teacher in Turkey. The interactions of a mathematics teacher and his students (n = 38) over two years were explored. The WhatsApp group increased interaction in out-of-school hours. Analysis of the teacher's communicative acts was the leading force that encouraged the group to continue to interact. The teacher portrayed an informal and sincere presentation of himself on social media. A constructive communication style between teacher and students was fostered by connecting through WhatsApp in out-of-school hours, when the teacher's informal communicative acts have facilitated their learning.