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.