Sylvester Stallone states on the commentary that Church's line, "You guys aren't gonna start sucking each other's dicks are ya," was ad-libbed by Bruce Willis. He at first had reservations about the line but decided keep it in the movie.

Mickey Rourke said he did this film as a favor to Sylvester Stallone, who years earlier, when Rourke was in a career slump, offered him a major role in Get Carter (2000) and helped to pay part of Rourke's salary himself.

The role of Mr. Church, the man who hires the Expendables, was very difficult to cast. It was initially offered to Arnold Schwarzenegger, who declined in favor of a smaller cameo due to his political career. The role was then offered to Kurt Russell, who declined as he was not interested in "ensemble acting at the moment." Sylvester Stallone spent several months after principal photography determined to find a big action name for the part. The role was finally taken by Stallone's friend and fellow former "Planet Hollywood" co-owner Bruce Willis, who was busy filming Cop Out (2010) at the time.

Sylvester Stallone sustained fourteen injuries making this movie, including breaking a tooth, rupturing his ankle, and getting a hairline fracture in his neck that required the surgical insertion of a metal plate. He also had bronchitis and shingles during the shoot. He later said he never fully recovered from the injuries, "It did such a number on my body, I've never been the same. Never."

In the audio commentary Sylvester Stallone reveals that in the final battle, Steve Austin almost lost his leg due to an explosion that went off next to his foot. What saved him was the bag he was holding took the bulk of the blast. The bag acted as a shield when the explosion happened. (You can see this happen at the 1:24:05 mark in the movie.)

Continuity

When Barney sits down to let Tool finish his tattoo, the letters on his back only spell "EXPEND". It then takes Tool about 15 seconds to finish the word "EXPENDABLE", in between talking to Barney and Lee who came after they started.

Throughout the car chase with Gunner the front bumper of the black pickup, driven by Barney Ross, several times changes from totally missing to half broken and later to almost brand new.

When Barney Ross and Yin Yang stop by a traffic light just before the car chase with Gunner Jensen, the car behind them slows down and stops. When the camera changes angle the same car is seen from a distance slowing down and stopping again.

When Paine hits Sandra we can clearly see her face bruised, but later when he takes her to the torture room the bruise is gone.

The final time that Barney Ross gets into the cockpit of the plane, he gets into the seat while wearing a tactical vest. When he is shown from the front, he no longer has the vest on, but is wearing a t-shirt.



Factual errors

Several problems with the Fly & Die scene: Christmas turns left and fires the flare slightly out from the plane, but in the reverse shot the flare is coming from the right side of the plane. A flare is slower than the plane, meaning that firing it backwards would still make it fly in the direction of the plane, only slower. The flare passes through the cloud of flammables, but doesn't ignite it. The explosion stops at the end of the pier for no reason, even though the highly flammable cloud extends beyond the pier all the way to the plane.

The silver badge on General Garza's right breast is actually a United States Army Combat Action Badge. It is awarded to non-infantry soldiers who have actually engaged an enemy force in combat, and worn on the left breast. Since it would be nearly impossible for a foreign general to earn a CAB legitimately, the costume department most likely simply picked out a random military badge.

When Hale Caesar pulls out his straight razor, the blade - engraved with his name - is misspelled "Ceasar".

Igniting the fuel dump with the flare gun would have blown up the plane since they did not stop the fuel dump before firing the flare.



Incorrectly regarded as goofs

Though Vilena has Spanish as its primary language, Portuguese signs can be seen in many scenes. Since it's a fictional place, we can allow that both languages are common there.



Revealing mistakes

When the seaplane turns to the right immediately after takeoff from the island's port, there is no movement of the ailerons. This scene is clearly CGI.

When Christmas is videoing the island, he doesn't turn the camera "ON"; then he leaves the lens on "MF" i.e, no Auto Focus, so no focused video was possible.

During the the first ambush on the cargo ship the Expendables' targeting lasers are clearly CGI where the red laser produces a very visible spot of light on the skin.

As Ross and Christmas are leaving the island on their first trip, they shoot at the docks which are soaked in gasoline. In one shot we see the explosion clearly expanding horizontally several feet off the pier. On a bird's eye view shot we see a boat next the the burning pier clearly not affected by the blast or the fire.

A1 0:42:04 -after Barney climbs through the airplane hatch there is an opaque screen covering the opening.



Miscellaneous

Once Barney and Christmas are taken near the presidential palace by Sandra and they get out of the car, a sign is shown that reads "?rea Militar, Prohibido Passar." The word "passar" has a spelling mistake and it should be "pasar."



Audio/visual unsynchronized

When Barney is firing his sidearm at incredible speeds during the final shootout, the sounds of the gunshots come much faster than he can be seen pulling the trigger. Furthermore, he fires far more rounds than the Colt pistol can hold between reloads.

Rounds fired could be due to the possible use of a Para-Ordinance P-14, a Colt 1911 clone w/ 14+1 capacity. One scene appears to show a wider magazine and grip than a standard Colt 1911.



Crew or equipment visible

In the basketball court scene when Christmas is fighting Lacy's boyfriend, he shoves a basketball onto his chest and proceeds to stab it. A chest protector is clearly visible under the basketball and covering the stomach.

In the sequence while Sylvester Stallone and Jet Li characters are talking in a car while Stallone is driving, you can see the camera lens reflected in the back windscreen in almost every scene.

Just after the Expendables decide to return to Vilena, there is shot of trucks driving into the General's compound. As the trucks pass by, the shadow of the camera is visible.



Plot holes

After the waterboarding scene, Sandra is taken away by General Garza and his men, but later when Munroe visits Garza, he has somehow managed to retake possession of Sandra, even after Garza clearly had his daughter in custody earlier and would not have likely just given her up to Munroe after what that waterboarding incident.



Character error

When Hale Caesar pulls out his straight razor, the blade - engraved with his name - is misspelled "Ceasar".

At the church, Schwartzenegger's character tells Willis' character to give the job to his friend, since he "loves playing in the jungle". There don't appear to be any jungles on Vilena, or at least the mission doesn't take place in one.