The release of Wii Party in 2010 was a rather confusing event. The game was developed by members of the Mario Party development team, leading many players to believe the series was finished after eight main entries and two handheld spin-off titles. The fact that a new Mario Party game hadn't been released since Mario Party 8 in 2007 raised even more suspicion as to the overall fate of the franchise, especially since Mario Party releases were like clockwork in the late '90s and the '00s. Fans, however, were happily proven wrong when Nintendo announced Mario Party 9 at E3 2011.

Mario Party 9 retains the board-based mini-game formula that made the series very popular. Up to four players can pick from the cast of 12 characters to join in and move around one of the seven stage-like boards. Instead of collecting coins and competing for stars, however, Mario Party 9 simply has each participant vying to collect as many mini-stars as possible. The boards, which each sport a different Mushroom Kingdom theme, often have unique tricks, traps, and obstacles that change the course of the game, keeping players mindful of their strategies.

Instead of plotting their own course across a board, players now travel together in special vehicles across the stages, with the participants taking turns playing the role of captain to drive the vehicle and pick up any mini-stars it moves over (or lose mini-stars by landing on "mini-ztar" spaces). Boards now have a clearly defined beginning and end; in the past, a course would just loop once players reached the starting point after traversing it. Now, the objective is to reach the end of the board, where players engage in a competitively cooperative effort to defeat one of six stage-specific bosses (each stage also includes one of six unique mini-bosses). Mario Party DS implemented a similar feature—where after a few rounds the player with the most stars would go on to face the boss—but Mario Party 9 is the first game in the console series to feature the concept.

Once a player lands on the respective space, the group gets to play a mini-game. There are over 80 new mini-games in this iteration of the Mario Party series spanning five categories (Free-for-All, 1-vs.-Rival, Bowser Jr., Boss, and Extra), as well as seven unique mini-game experience variants in Mini-Game Mode.

A common complaint levied toward the Mario Party series is that gameplay progression is slow. Mario Party 9 seeks to remedy this problem by including seven unique mini-game experience variants in Mini-Game Mode, where players can jump into the activities right away if they don't have time for the full board gameplay or have no desire for the extended gameplay sessions. Mario Party 9 also rewards players for going through the game up by giving them Party Points, which are used to unlock new modes and mini-games outside the main game.