You need action replay which you can find at game stop. then you scroll down and find more master balls. I don't have the code though, sorry but there is one of the wiki answers where it tells you the code. it's how do you get 98 master balls? I hope it helped!
ACTION REPLAY
There is only one master ball in Pokemon diamond. But there is a cheat for getting a WHOLE lot more. Look it up at how do you get 98 master balls? I don't know where the master ball is I think it's in a team galatic headquarters.
you dont......you have to cheat but i am still trying to figure out how.
To get more than one Master Ball, you must trade Pokemon that are holding them to your game.
In Pokemon Diamond, Pearl and Platinum you can get one master ball from Master Cyrus. To get more, you have to cheat using a Action Replay DS or DSI, or you can trade Pokemon with your friends and receive master balls from the Pokemon that they traded.
u cant
Have your friends trade you the master balls they got.
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You can't get more MasterBalls. You can only get one, unless you get very lucky playing the lottery ticket game in JubilifeCity.
well the max of master balls you can get is 999 but you can only get more master balls in trades.
No
In each game, there is only one master ball obtainable. However, you can get more master balls with an Action Replay device, or by hacking the game, or by trading over a Pokemon holding a master ball from another game.