Mummy Punjabi is the story of a mother who has deal with changes in life when her children get married. Babyji a.k.a Mummyji (Kirron Kher) is a modern mother who lives in Chandigarh with her husband (Kanwaljeet) and their three adult children. While she gives full freedom to her young daughter (Simran), Mummyji is rather protective about her two sons. One son (Sachin Sharma) is a doctor and the other (Viraf Patel), a restaurateur. Mummyji dreams of marrying off the doctor-son to an NRI girl, while she wants a homely girl for the other son. In spite of her husband's pleas, she gives her daughter a free hand to do whatever she wants.
A Sikh bachelor (Jackie Shroff), who was Mummyji's college classmate, stays close to their house and often visits the family. Her husband takes this in good humour as he is also friends with the bachelor. A maid (Divya Dutta) is the gossipmonger of the housing society.
Soon, Mummyji finds suitable brides for her two sons. To her surprise, the bride, who seems to fit into her criteria for her daughters-in-law, reveal their true colours after marriage. While her homely daughter-in-law breaks into an outrageous dance at her other son's wedding, her NRI daughter-in-law turns out to be a cheat, who was trying to swindle the family! However, life soon returns to normalcy as the daughter-in-law come around. Next, Mummyji also discovers that her son has actually been operating a night-club and had lied to her about running a restaurant. Mummyji is aghast but takes it in her stride. Soon, both her sons and their wives leave for the US for better prospects. An ageing Mummyji and husband are left behind alone with the daughter. Mummyji's bachelor-friend also gets married. Even her daughter finds a good suitor and marries him. What happens next? Does Mummyji continue living life as she always has, or does her life changes? What about her children and their spouses? The rest of the film and the climax answer these questions.