
Sid (Rahul Bose) is a short, thirtyish DJ, who finds himself playing music at Trisha's (Mallika Sherawat's) marriage to Vivek (Jas Arora) in Delhi. However, he witnesses her fight her sense of responsibility and duty towards her parents and the groom, and runs away.

Six months later, he meets her again at a DJ competition in Mumbai, which he has just lost, yet again. Before you know it, they're in a relationship, and three years have passed. Trisha thinks she is ready for marriage, and gets down on her knee to propose to Sid. Sid suffering from the typical commitment phobia, is at a loss for a reasonable answer. In a bid to not lose her, Sid finds himself engaged.

But along with the engagement comes a new set of problems - such as shopping for furniture for their home, engagement rings, and more importantly facing the father of the bride! The father has more than one problem with Sid. He doesn't have a future, he earns a lot less than Trisha, and he doesn't seem responsible enough. Over an altercation Sid has with Trisha's father, the couple break up. Vivek is waiting in the wings, to help mend her broken heart. Sid on the other hand, finds himself being wooed by item girl, Tanya (Sophie Choudhary), star of the 'Baby Girl vol. 3' video.

After a few amusing run-ins, an attempt to be just-friends, and a sad-song ("Jaane Kya" sung by Zubin), Sid, finally realizes, thanks to his mother, that his commitment phobia is the result of a childhood scar. His father abandoned Sid and his mother, when Sid was very young. His mother reassures him, that he is nothing like his father, and would make a great husband. But it's too late, Trisha has already agreed to marry Vivek. This leads him to Trisha's dear friend Anjali (Suchitra Pillai), who reminds him of Dracula because she always attacks him, for making Trisha unhappy. She helps him crash Trisha's wedding party.

The climax builds up, as Sid's job involves not just convincing Trisha that his hang-ups have abated, but also avoid a deadly confrontation with Trisha's father.
Mallika Sherawat as Trisha Mallick
Rahul Bose as Siddhant "Sid" Roy
Ranvir Shorey as Narayanan "Nanu" Iyer
Sophie Choudhary as Tanya (Baby Girl Vol.3)
Suchitra Pillai-Malik as Anjali (Dracula)
Sharat Saxena as Retd. Major Gen. Veera Bhadra Mallick
Tarana Raja as Shalini
Aamir Bashir as Kapil
Jas Arora as Vivek Chaddha
Sapna Bhavnani as Nina Manuel
Shabnam Kapoor as Trisha's mother
Pyaar Ke Side Effects, the album was released on 20 June 2006. It consisted of 6 Original songs and 3 Remixes composed by Pritam. It garnered generally Positive reviews from the critics. Narbir Gosal from Planet Bollywood rated the album 8/10 and wrote "Pritam has put together five good compositions on this album, but the pointless remixes and three versions of one song dilutes the impact. 'Pyar Karke', 'Jaane Kya' and 'Is This Love' stand head and shoulders above the rest, and on the whole this album is a definitely worth the buy."
All lyrics written by Mayur Puri; all music composed by Pritam.
Pyaar Ke Side Effects was a modest box office success, earning 74.7 million. The film garnered mixed reviews from critics. Several critics, such as Indiafm's Taran Adarsh felt that the second half of the film "drags".
The Pyaar Ke Side Effects team announced a sequel Shaadi Ke Side Effects in June 2012 with Vidya Balan and Farhan Akhtar in the roles of Trisha and Sid. All the other technicians returned for the sequel along with the director and music director. The film was released on 28 February 2014.