Thanneer Mathan Dinangal follows the life of a sceptical yet honest eleventh-grade student, Jaison. The boy has a huge crush on Keerthy, his classmate but unfortunately, she does not reciprocate his feelings. Matters worsen when their new Malayalam teacher - Ravi Padmanabhan - becomes the centre of attraction. Ravi's influence on everyone irritates Jaison and he openly complains about Ravi being a fraud. As the film progresses, Ravi's true identity is revealed while Keerthy and Jaison fall in love. Experience the mischievousness during school days, teen angst, and a whole lot more in this coming-of-age drama.