One or two years following his defeat, Shang Tsung begs his master, Shao Kahn, to spare his life. He tells Shao Kahn that the invitation for Mortal Kombat cannot be turned down, and if they hold it in Outworld, the Earthrealm warriors must attend. Kahn agrees to this plan, and restores Tsung's youth. He extends the invitation to Raiden, who gathers his warriors and takes them into Outworld. The tournament is dangerous, as Shao Kahn has the home field advantage, and an Outworld victory will unbalance the furies and allow Outworld to subsume Earthrealm.

Mortal Kombat II follows Mortal Kombat and precedes Mortal Kombat Trilogy.

It seems to have been replaced storywise by Mortal Kombat: Shaolin Monks, though many argue that this game has many contradictions to the events in the Mortal Kombat storyline, and, as such, should not be considered canon.

In the arcade version, the 250th two-player game would unlock a session of the arcade classic Pong.

After landing a strong uppercut against the opponent, the face of Dan Forden, a lead programmer, would appear in the lower-right corner of the screen and shout, "Toasty!" In the Portal stage, if the player very quickly held down and hit the start button before Dan's head left the screen, they would then instantly begin a new stage against a secret character named Smoke, a grey recolor of Scorpion. However, the Genesis version includes an alternate Toasty image: By activating the cheat menu in the options screen, Dan Forden's face is replaced by one of Probe Entertainment's (the team responsible for the Sega Genesis version) programmers. The "Toasty!" sound remains unchanged. Toasty has become one of the best-known video game easter eggs, among the likes of dopefish. Many games have included their own versions of Toasty, such as StepMania, in which a character pops out and sings "Toasty!" after a long combo of perfects.

Another secret character was named Jade, a more dangerous green recolor of Kitana. To fight Jade, a player would have to defeat their opponent before the mystery "?" stage using nothing but low kicks. In the Living Forest stage, both Smoke and Jade could sometimes be seen peeking from behind the trees as a clue to their existence as hidden characters.

If the player won 50 consecutive fights he/she would come face to face with the black ninja Noob Saibot, which originates from the last names of the lead designer John Tobias and lead programmer Ed Boon spelled backwards.

After knocking the victim into the acid pool, hold down on the joystick. Dan Forden will say "Ow-a" or something similar.

Press down on any joystick during the attract mode to bring up the top 15 players.

On the Kombat Tomb stage, hold down on both joysticks immediately after knocking the victim into the spikes. The victim will gradually slide down the spikes.

Two non-existent hidden characters were "Torch", and "Hornbuckle." In Mortal Kombat II there is a location called The Pit II. Far in the background of this stage there is another bridge across the chasm. Standing stationary on this bridge are two fighters: one of them is a Liu Kang sprite with green pants who was named Hornbuckle by fans. One of Jade's hints was "Hornbuckle who?", which people thought was the name of a hidden fighter, and was apparently given to the guy opposite "Torch" on the Pit II. If you watch the ending credits, one of the programmers' last names is Hornbuckle. The other fighter is a humanoid character that seems to be made of fire. As these two characters never move, it has been suggested that the "other fighter" is actually a funeral pyre. Finally, there is a cloaked figure who floats in front of the window during fights in The Tower and Portal stages in MK2. This character was dubbed Cloak by fans, and was assumed to be a hidden character. The character of Torch, who had been very popular with fans, eventually showed up as a playable character in Mortal Kombat: Deadly Alliance. Unfortunately, due to trademark issues, he had to be called Blaze instead of Torch. The true identity of Cloak was revealed in Mortal Kombat: Shaolin Monks to be one of Shang Tsung's servants, a shadow priest.

On the Dead Pool stage, with Sub-Zero or Shang Tsung morphed into Sub-Zero, deep freeze the opponent (F-F-D-HK) and then proceed to shatter the victim (F-D-F-F-HP) but press LP + LK immediately. If done correctly, the screen will turn dark and the victim will fly into the acid (see first pic on right) This trick also works with Johnny Cage's Head uppercut (F-F-D-U).

On the Armory stage, with Reptile or Shang Tsung morphed into Reptile, do the tongue fatality and watch the floor move.

With Shang Tsung, morph into Sub-Zero and keep deep freezing the victim till you morph back. Then quickly morph into Jax and do the head smash fatality. The colour map of the victim will get screwed up.

On the final battle with Shao Kahn, catch him with Kitana's fan lift when the timer runs out in the winning round. The machine will play the exploding sound of Shao Kahn and then it will lock up. A good way to earn a free credit

Mortal Kombat II is usually considered the best game in the series.

Mortal Kombat II was so popular when it hit the arcades that several of the machines were later installed with deadlock security panels on the back to prevent theives from ripping the game's motherboard straight out of the machine and taking it home (pictures of an arcade fitted as such are available as unlockable images in Mortal Kombat: Deadly Alliance).

After the low sales of the SNES version of the first game against the Genesis version, Nintendo didn't censor the blood and fatalities as they did before in the US and UK SNES version of Mortal Kombat, although they slapped a warning label in the front of the game box. The Japanese version is censored to a degree, with green blood for all fighters, as well as the screen colors turning black and white for fatalities. As a result, the SNES version sold much better than any other version and was considered at that time the best port of the arcade version.

Mortal Kombat II's levels and overall place within the Mortal Kombat timeline serve as the basis for the action/adventure game Mortal Kombat: Shaolin Monks.

Mortal Kombat II was re-released in its arcade perfect form in 2004 as a part of Midway Arcade Treasures 2. It is also unlockable via a secret code in the game Mortal Kombat: Shaolin Monks.

In Japan, Mortal Kombat II was released on the PlayStation. This version is extremely rare, and commonly goes for over $100 on eBay.