One Two Three revolves around three Laxmi Narayans who create a lot of confusion because of the similarity in their names. In addition to that, Diamonds worth ten crores are stolen from a certain Don, Papa. The diamonds accidentally fall in the hands of young lovebirds - Chandu (Upen Patel) and Chandni (Tanisha), who quickly hide them in a car. Papa and his idiotic henchmen Albert (Vrijesh Hirjee) and Pinto (Manoj Pahva) are desperately hunting for the diamonds while hot headed police officer Mayavati Chautala (Neetu Chandra) is on the prowl looking for offenders of any kind.
The first Laxmi Narayan (Tusshar Kapoor). He's from a ‘khandani’ mafia family and his mother prays that with a few murders under his belt, he will be settled for life. The second Laxmi Narayan ( Sunil Shetty) is a loveable geek who takes pride in being accurate and detailed. He'll do anything to please the boss, including bearding a Don in his den. Lastly, the third Laxmi Narayan (Paresh Rawal), all the Bhabhis and Behenjis of Delhi will vouch for his uncanny eye - Just one look and he can gauge your innermost measurements. But then he comes across Laila (Sameera Reddy) who refuses to show him what he wants and blackmails him instead!