The preview for this film was banned in some theaters for scaring teenagers and small children viewing PG-13 films.

The events of Paranormal Activity 2 take place before the events of Paranormal Activity (2007) (beginning two months before and following up with the events depicted in the original film) which technically makes it a prequel. Such is true with Paranormal Activity 3 (2011), which is a prequel to the both of them. Paranormal Activity 4 (2012) is really the first sequel, chronologically speaking, to the original.

Upon release, this broke the record for the biggest midnight gross of an R-rated movie with $6.3 million, and the biggest opening for a horror movie of all time, earning a total of $41,500,000 in its opening weekend.

The trailer for Paranormal Activity 2 used a lot of footage that didn't appear in the movie. This angered many fans, but the directors said "they had to" because of the storyline.

(at around 1h 16 mins) During the climax, immediately following when the power goes out in the house, there is a single, out of focus, frame of Hunter crawling in the street that quickly flashes on and off screen.

On the official site for the film, there are secret messages when the trailer is fast-forwarded or rewound. Additionally, after the trailer finishes playing, the baby appears in the mirror but isn't present in the nursery. Also in the mirror, letters written in what seems to be blood spell a message. Upon flipping the picture horizontally, the message reads, "What is happening to Hunter?"

Kevin Greutert was initially hired to helm the film but was forced to work on Saw 3D: The Final Chapter (2010) when the producers of that film exercised a clause in his contract, forcing him off Paranormal Activity 2 (2010).

This film was announced shortly after Paranormal Activity (2007) was released into theaters in 2009.

Shipped to theaters under the code name "Sharpie 79".

As with the first film, Paramount Studios utilized world-renowned paranormal expert, Christopher Chacon, to assist in internationally promoting and publicizing the film.

There are two Ramones and one Misfits poster in Ali's room. Daniel Rey, namesake of Brian Boland's character, produced albums for both The Ramones and The Misfits.

Brian De Palma, Akiva Goldsman and Kevin Greutert were all considered to direct.

Just like in the first Paranormal Activity, it has been confirmed that there is an alternate ending to this film as well; where Katie kills the baby boy Hunter by breaking his neck. According to the website Bog Bit, it was never shown to the public eye because it had been claimed as "too violent." They also quote: "For those die hard Paranormal Activity fans, they may be dying to see the alternate ending as well as looking towards a sequel, but this new ending is going to push a lot of viewers away."

Body Count: 2 (3 counting Micah offscreen).

Paranormal Activity 2 is considered a prequel to the original even though the events in both films occur almost simultaneously. The events of the first film can be considered to have started sometime before Katie's and Micah's visit to Katie's house and continued after Katie returns later for Hunter.