Na Jaane Kabse is a romantic comedy. Karan Bajaj (Garry Gill) is unhappy that his to-boy-wife, Preeti, has run away on the wedding day. At first keen to insult her family by telling the members that she had run away, he suddenly decides to tell them that he has called off the marriage. Obviously, the girl's family members beat him up and he has to beat a hasty retreat from there. He meets a girl, Anjali (Amrita Prakash), and befriends her.
Karan is under pressure from his partner, Ravi Sood (Ayub Khan), to get married anyhow and come with his wife for honeymoon at the resort which they (Karan and Ravi) own jointly. The plan is to call the media and impress them with the story that Karan had chosen his own resort for his honeymoon. This according to Karan and Ravi would act as a great promotional campaign for the resort which would then take off in a big way. Ravi is insistent that Karan get married and bring his wife because he fears, the landlady, Monica (Lillette Dubey), would otherwise cancel the deal. Karan asks Anjali to pose as his wife for three days so that they could get great media mileage out of their honeymoon at their own resort. Anjali agrees.
Once at the resort, Anjali is shocked when Monica introduces Karan to one Dayakar Premkar (Sharat Saxena) who is actually her (Anjali's) father. Dayaka, can't believe that anybody could fall in love with his daughter and marry her as he had, all along made her look unattractive so that no boy would fall in love with her. This was because he wanted Anjali to marry Akshay, a boy of his choice. Anyway, Dayakar vows not to allow his daughter to consummate her marriage. After the press conference and the wedding reception, he orders his daughter to return home with him. Does Anjali oblige? Or does she decide to marry Karan as both have, by now, fallen in love with one another? Does Dayakar get Anajali married to Akshay?