HUM DO HAMARE DO is the story of a man who gets fake parents to impress the girl he loves. Dhruv Shikhar (Rajkummar Rao) is an orphan who used to work in the dhaba run by Purshottam Mishra (Paresh Rawal) as a child.
One day, he runs away and studies hard. He then emerges as a successful entrepreneur and the creator of a VR app called Jaadugar. At the launch event of his app, he meets Anya Mehra (Kriti Sanon), a vlogger. He falls for her and she too starts liking him. However, she wants to marry a person who has a sweet family. She also has a reason for doing so. Her parents died when she was a kid. Her chacha Dr. Sanjeev Mehra (Manu Rishi Chadha) and wife Rupa Mehra (Prachee Shah Pandya) raised her like her own child. Dhruv fears that if he tells her the truth that he has no one in this world, she might leave him. So he lies that he stays with his parents. Anya agrees to marry him.
Then he along with his best friend Shunty (Aparshakti Khurana) decides to find a man and woman who can pretend to be his parents. Shunty takes him to Shadiraam (Sanand Verma). He is an expert wedding planner and can also help in getting fake guests. He lines up hundreds of men and women for Dhruv's requirements. Sadly, none of them fit the bill. At this point, Dhruv is reminded of Purshottam who has now retired and has settled in Shimla. He also realizes that he's in love with Deepti Kashyap (Ratna Pathak Shah), who also resides in Shimla. Purshottam is aware that she's living in the same city but is scared to approach her.
When Dhruv learns that Deepti is Purshottam's old flame, he convinces her to be her mother. She agrees and once she's on board, Purshottam also follows suit and agrees to be his father. Anya's family and Dhruv's 'family' then meet at a restaurant. All is going well until Purshottam has too many drinks. He gets so emotional that he asks for Deepti's hand in marriage. An aghast Deepti leaves. Someone in the restaurant shoots the video of the proposal and it goes viral. This embarrasses Dr. Mehra and he now has second thoughts on whether he should allow Anya to marry into such a family. What happens next forms the rest of the film.