[4] Hari (Darshan) and Umapathy (Dheena) come to Top Slip to paint a tiger statue and colorfully design a well-located mountaintop.

Then, there is an aspiring young wildlife photographer named Varsha (Keerthi Pandian), who gets special permission to click pictures inside the forest.

The rest of the film is all about how Hari, Uma, and Varsha, with the help of local people, save Thumbaa and its cub from the forest officer and his gang.

"[8] A musical promo video of the film was released on 21 February 2019 in Tamil by actress Keerthy Suresh, Telugu by actor Sai Dharam Tej, Malayalam by Nivin Pauly and Hindi by rapper Badshah.

The promo was unveiled on YouTube and crossed 1.5 million views within 24 hours and gained positive reviews among the audience in the social media.

[4] M. Suganth of The Times of India gave 3 out of 5 and wrote, "The film might entertain kids, but for the adults who accompany them, it might engage only in parts because of the uneven narration".

[14] Sify stated, "Thumbaa is a film which will be surely enjoyed by kids but the makers failed to attract all age group audiences mainly because of the weak writing".