Peace Walker was originally named "Metal Gear Solid 5: Peace Walker". The number "5" was dropped later on, but Kojima personally directed the project, and considered it to be "an MGS5-class game".

In the Main Ops mission, "Infiltrate the Crater Base", series creator Hideo Kojima can be found in the truck with the license plate "63824". Finding him will automatically recruit him to Mother Base.

Originally, Kojima was not going to be a part of the creation of the game aside from providing the overall guidelines and concepts for the project. However, he noticed that the team did not understand the story's themes about nuclear deterrence and the cold war (admitting that it was most likely because of generational differences) and stepped in to make sure the game turned out how he envisioned.

The character "Cécile Cosima Caminades" is based on the French Communications Manager of Konami, "Cécile Caminades".

In the mission, "Dead Man's Treasure", The End from Metal Gear Solid 3: Snake Eater makes a cameo by "contacting" Big Boss from the grave via the Codec (frequency 0.00).

According to director Hideo Kojima, Kaz's design in Peace Walker was partly based on the captain from the film, "Westworld", although the development team had never heard of the film.

On Main Ops 16, the player can get onto the roof of a miner's shack and trigger a special button prompt that, when pressed, has the player jump with their arms spread into a box full fo straw, accompanied by the sound of an eagle's cry. Once the player has completed the Leap of Faith, Kazuhira Miller explains the history of the "Assassin's Straw Box," stating it was used by an order of assassins in the time of the crusades. This is a reference to Assassin's Creed and the Leap of Faith the assassins do. The box is then unlocked for use in future missions. The box even allows the player to knock out guards while hiding in it, similar to how Ezio could assassinate guards from a bundle of straw.

The torture scene in which Dr. Strangelove electrocutes Snake with a lightning rod was altered from the original Japanese version. In the Japanese release, Dr. Strangelove uses a "Laughing Rod" to torture Snake.

EVA's English voice actress in Metal Gear Solid 3: Snake Eater and Metal Gear Solid: Peace Walker was credited under the name Suzetta Miñet. Fans widely assumed that this was a pseudonym as she had no other credits in anything, which sparked years of speculation as to who she could be. One of the most leading theories was that EVA was voiced by Debi Mae West, the voice of Meryl in Metal Gear Solid and Metal Gear Solid 4: Guns of the Patriots. However, while West acknowledged that the characters sounded similar, she denied she was the voice of EVA in 2015. Konami would eventually confirm in a 2024 behind-the-scenes video promoting Metal Gear Solid Delta: Snake Eater that the pseudonym belonged to Jodi Benson, who was best known for voicing Ariel in Disney's 1989 adaptation of "The Little Mermaid". Benson explained that she used the pseudonym at the recommendation of the game's English voice director Kris Zimmerman Salter, because of her association with Disney and other family-friendly roles aimed towards younger audiences at the time. The name itself was based on a pet dog Benson owned in her childhood named "Suzette Monet".