The story of Chaahat - Ek Nasha revolves around Mallika Arora (Manisha Koirala) who is a pop star. She is madly in love with Rahul Kapoor (Aryan Vaid), the owner of RK music world. He also loves her from the core of his heart. However, when he proposes to her she politely turns down the marriage proposal saying that she doesn't believe in wedlock. She ardently follows the western lifestyle and is strongly of the view that the instant a couple gets married, the love-n-affection glides away from their lives. Though she is physically attached towards Rahul she doesn't want to tie the knot.

Story takes a new turn with the downfall of Mallika. Rahul launches a new comer Rashmi Jaitly (Preeti Jhangiani), an aspirant singer and dancer, in his new music video. Rashmi's debut music video is a big hit and she becomes a star overnight. Rahul gets attracted to her and she too looses her heart to him. Rahul decides to marry her.

When this reality of Rahul's falling in love with Rashmi is dawned upon Mallika she is shattered. It's a big emotional shock to her. It's at this juncture that she orders her personal bodyguard Jaidev (Sharad Kapoor) to knock off Rahul. However, the next morning when her alcoholic intoxication vanishes, Mallika realizes her mistake and calls up Jaidev in order to stop him from killing Rahul.

But Jaidev who is a one sided lover of Mallika, is all set to eliminate Rahul. The dangerous game begins... and Mallika wants to save her love at any cost...