Mario vs. Luigi is the main competitive form of multiplayer and has 2 players competing with each other in a battle for Big Stars. The basic premise is to collect the defined number of Big Stars as quickly as possible while preventing your opponent from doing the same. Controls are exactly the same as Mario Game. Getting damaged will cause you to lose a Big Star, and, depending on what you get damaged by, can power you down or kill you. A maximum number of lives can be set for a deathmatch. It can be played with either one or two game cartridges.
- 1: Upon selecting the option from the main menu, you will be asked if you wish to compete with someone who owns New Super Mario Bros., or someone who does not. Choose whichever is appropriate.
- A: If you are playing with someone who does not own a copy of the game, you will be asked which Mario brother you wish to play as; Mario or Luigi. The differences are cosmetic only, choose whichever you want.
- B: After choosing your Bro., you will need to have whoever you are playing with select "DS Download Play" from the DS bootup menu. After a brief period you will see this message: "(Username of other player+Bro. you did not choose) has appeared! Play a game?". If you want to play with the person, select yes. If not, press no.
- 2: You will be confronted by an options screen. The options are:
- Wins: How many wins are needed are needed to finish the match. Ranges from 1 to 3. Default 2, a best out of 3 game.
- Big Star: How many big stars are needed to win the game. Possible settings are 3, 5 (default) and 10. For longer games, select more stars.
- Mario/Luigi's Lives: How many lives the Bros. have. Possible settings are 3, 5 and Endless (default). Changing the lives from Endless can change the game from a star collecting race to a race to collect coins in the hope of getting a Starman, Mega Mushroom or Blue Shell to kill the enemy. For a truly deathmatch centered game, set Big Stars to 10 and lives to 3.
- Course: Determines the selection method for stages. Possible settings are Choose Each Time (default) and Random. Choose Each Time will make you choose the stage each time, Random will choose it for you. If you chose Choose Each Time you will have to choose a stage (see below for info). If you set it to Random, you will be plunged into one of the stages listed below.
- Grass Land: Modeled off the World 1-1 of the original Super Mario Bros., this stage is fairly basic. Player 1 should move off to the left, get the power-up, coins and Big Star (if it's there). Afterwards, stomp the Green Koopa, carry it's shell and fling it in the general direction of the opponent. Player 2, on the other hand, should move to the right, getting the power-up, Big Star (once again, if it's there) and take advantage of the greater number of coins. From there, anything can happen. Stage size: Medium.
- Block World: Modeled after the many underground courses, this stage is highly erratic. Gameplay consists mostly of frantic collection of coins and beating the Big Stars out of your foe. Consider yourself lucky if you get a Starman, extremely so if you get a Mega Mushroom. Although, if you do get a Mega Mushroom, heres a tip: Don't jump unless you want to die. A stray Koopa shell can deal a lot of damage to the stage and Mini Mushrooms should be avoided. Stage size: Tiny.
- Icy Waste: Modeled after World 5 in general, this stage involves traversing large distances while avoiding the Bullet Bills. The only thing notable is that this stage has more enemies than any other. Both players should head for the Blue Koopa (to the right) as quickly as possible as the Blue Shell it drops is crucial to winning the game. If you get the first shell you should focus on getting Big Stars and preventing your opponent from getting a shell. If you did not get the first shell, get only Big Stars that are close to you and focus on getting a Blue Shell of your own. Once both players have a shell, the winner will mostly be determined by where the Big Star spawns, however, one thing that can help a lot is the knowledge of how to fly (using the spring pad) at high speed. It is easiest to do with a Blue Shell (and how to is based on the Blue Shell) but it is possible in all forms other than Mega. Stage size: Huge.
- How to: Distance yourself from the spring pad and begin dashing. Once you are in your shell, let go of the D-pad (but not the dash button). Jump to land on the spring pad and then bounce off it. If performed correctly you will be traveling through the air at roughly twice the normal speed.
- Pipe World: Modeled after a stage in World 7, this course is strange due to the fact that wall-jumping gives a huge advantage. Mini Mushrooms can be beneficial on this level due to the increased length of your wall jumps. As Mini Mario, you are able to wall jump to above the level at either end of the level. There are also coins available on top of the level. Despite the large number of pipes only 2 can be warped through. Stage size: Small.
- Splat World: Modeled after several towers/castles, the stage probably has the highest fatality rate of them all. Gameplay is slow and semi-strategic, with players having plenty of time to plot their next move while they are trapped in one of the small alcoves. Consider yourself dreaming if you get a Mega Mushroom. Consider yourself extremely lucky if you get a Mini Mushroom, but if you do, stay away from fireballs. In the middle of the level, there is part where only Mini Mario can enter. Inside this section, there are 4 coins. Above those 4 coins is a bridge which you can jump through from the bottom. There is also a way to get in here without a Mini Mushroom. Stand on top of the bridge, when the ceiling comes down hold down and start jumping. Stop ducking as soon as the ceiling touches you. You will fall through the bridge which will allow you to retrieve the coins below, or attack you opponent. Stage size: Large