One Fine Monday revolves around Shyamrao Sawant (Shekhar Suman), one of the most feared and powerful dons in the city. After committing to his father on the deathbed that he will give up his present trade and reform, we pick him up on one Monday morning that will ensure that he goes legit all the way. As the fateful Monday progresses, Sawant if forced to come to terms with a pregnant sister (Gauri Karnik) who is not really pregnant, a thieving accountant (Raj Zutshi), an extremely temperamental wife (Tanaz Currim), the personification of the strong arm of the law that is out to get him (Rajesh Vivek), a perplexed and eccentric scholar (Himanshu) and a sister he never knew he had (Tripta Parashar).

On Monday that was supposed to set everything right, Sawant is found running from pillar to post trying to lead the life of an upstanding citizen but what is to become of him at the end of it all is a story unto itself…