All cheats for this game by platform: Wii
Downloadable Wii Sports Cheats
91 Pin Strike in Power Bowling Training
To get an automatic 91 pin strike in the last round of Power Bowling, Throw the ball on the right or left rail (depending on if you are right or left handed) so that it stays on it the whole time. If it reaches the end without falling off, you will hear a "click" and an explosion. Then all the pins will fall down from the shockwave. NOTE: This only works on the last round.
While playing tennis, after you pick your character click on the one in the first row. It turns into a ? When you start the game a computer player will show up. You can also click on the computers charaters and turn them into yours. If you do the game screen will go split screen but if your faceing your own characters you control them so you could make your side win easier.
If you jab the numchuck to left while curving it, it will hit them on their side.
When playing Wii baseball and you are batting hold down [B] and [A] at the same time to make your hit more powerful. If your pitching, press the two buttons to pitch under hand. Press the  button to pitch overhand again.
Change bowling ball color
As The screen is fading to black for bowling, hold down the control pad until it fades to bowling for these colors:
Control Pad Up - Blue Ball
Control Pad Right - Gold Ball
Control Pad Down - Green Ball
Control Pad Left - Red Ball
Change the tennis court
To change the tennis court to the blue practice court, press and hold  at the warning screen that shows after selecting characters.
Play Golf without maps or meters
To disable the power meter, map, and the wind speed indicator, press and hold , then make a selection at the "Select a Course" screen.
Unlock Special Bowling Ball
Get to pro level to unlock a bowling ball with diamond designs on it.
Silver Boxing Gloves
After you've beaten the Grand Champion, Matt, in a boxing match you'll be able to wear silver boxing gloves. To do so, hold (1) when the screen becomes black before a boxing match.
During Target Practice, (Tennis), If you don't hit the target, you will hit the brick wall around it. This will make the section of the wall you hit darken slightly.If you darken it enough, the bricks start breaking. Soon, after you break enough bricks, there will be a large hole.
Glitch: Knock down other players pins in bowling
This is best done on 2 player mode but I hear its possible by yourself. In bowling, if you aim your arrow to the very end of the lane, then move your character to the end aswell, you can throw the ball onto the other players lane, most likly it will go in their gutter, but if your talented enough, you can get it to knock down their pins. This even coiunts on your score!
While pitching, press  before throwing. To return to normal pitching press .
Getting pro in either tennis or boxing
If you get pro, which is over 1000 points, then in either sport, the reward is a bigger audience, and all of your Miis that aren't being played get put into the audience. If you make a bunch of random Miis, they will all be there.
Easter Egg: Amuse Crowd in Bowling
To make the crowd laugh in bowling, move to either of the gutters in your lane, turn into opposite lane, and bowl so the ball goes over the barier between the lanes. The ball will go into the gutter in the opposite lane and the crowd will laugh.
Easter Egg: Scare Crowd in Bowling
To scare the crowd while bowling, start the regular motion for bowling and let go on the backswing. The ball will fly backwards and the crowd will scream and jump.