BMX Plus is a Plus Event that appears in the Nintendo 3DS version of Mario & Sonic at the Rio 2016 Olympic Games. The objective of the event is to complete the course in the fastest time. The playable characters in this event are Mario, Waluigi, Dry Bones, Sonic, Metal Sonic, Wave and Mii, with Wave being unlocked by beating her in the event on the fifth day of Mario's story in the Road to Rio mode. Toads and Chaos appear as referees in this event.
In this event, the player stats by pressing after the three second countdown. If the player presses too early, they will have a slower start. Once the event has started, the player must repeatedly press to speed up, and can move their character left and right using either or . The faster the player presses , the faster the character travels. When the player reaches a jump, they must press as close to the edge as possible to perform a jump, with the closer the player is to the edge of the jump when taking off giving them a larger speed boost and more air time. They can also use to jump onto rails, which allow them to travel at a faster speed without pressing , but they can be knocked off by the other players. The rails can be jump onto at any point along them by simply pressing . The player can also perform a Super Dash by repeatedly pressing when their Super Dash gauge is full enough, which grants them a short boost of speed each time is pressed. The gauge slowly fills over time, but can be filled faster by performing successful jumps. The player can also collect Rings throughout the course, which allow them to reach a greater top speed the more of them that are collected, but can be lost by hitting walls, opponents and obstacles on the track. Aside from standard jumps and rails, the course also features a number of other obstacles throughout, including Piranha Plants in Warp Pipes, which will bite at the characters and cause them to slow down and lose Rings if hit, Goomba Towers, which either remain stationary or slowly move left and right and also cause the player to lose speed and Rings if they hit them, but are knocked over once hit, and Dr. Eggman-themed crates, which are stationary obstacles that are destroyed when hit and cause the player to lose speed and Rings. The track also features Dash Panels, which give the player a speed boost when moved over and also come in stationary and moving varieties. The track also features a large jump with several Dash Panels leading up to it, as well as a rainbow colored ring in the air which allows the player to perform much larger jumps and gain a significantly greater speed boost from them.