The party is going to be held at Thomas' house because his parents will be out of town. Thomas is, of course, very nervous about having the party at his place and potentially getting in trouble but his friends convince him that this is the best idea. Reluctantly, he goes along. The party is planned and things quickly spiral out of control. Hundreds of people show up at the party because one of the boys put ads on Craigslist and radio stations. The high-schoolers drink and smoke weed. Someone discovers a cache of Ecstasy tablets which lead to more and more people acting crazy. The cops are called several times but the partygoers manage to convince them that nothing is amiss.
The party results in a lot of damage to Thomas' home and his parents are forced to use his college fund to pay for it. However, they end up being happy that Thomas at least has friends and his goal of increasing his popularity with the party came true.
The film is a comedy and it is presented in the format of a home video. The producers wanted viewers to feel as if they were guests at a real party. Most of the actors in the movie are making their debut in Project X. Very few of them already had acting credits to their name. Because of the way the movie was filmed, it feels as if it is happening in real life and it feel as if the kids are real kids throwing a wild party. Even the actors were given mini cameras to film as they went around the fake party to add to the release. Project X is comedy filmed in the documentary-style.