Can you get Arceus in Pokemon Diamond?

Answer 1

Yes. To get Arceus, you must get an Azure Flute. They are obtained by special Toys R Us events or an Action Replay. Then, go to Spear Pillar and lay the Azure Flute. A staircase will appear. Walk up it and there you will find Arceus.

~Answer was from the one-and-only PokeNerd Ashmoon12~
yes like this

1. Go to Jubilife City.
2. Go to the third floor of the Jubilife TV Station.
3. Talk to the man by the set. He will want to interview you.
   • These words are different for each language version.
   • When he asks you a second part of the question say 'Wi-Fi' and 'Connection'.
4. When he asks you a question on the first part say 'Everyone' and 'Happy'.
5. He will then say that the mystery gift is on the Main Menu.
6. Go to title screen and click on Mystery Gift.
7. Choose Get Mystery Gift and then choose receive via wireless.
8. Use your gift and receive a SHAYMIN, MANAPHY, DARKRAI, or ARCEUS from a Nintendo Event.

• Usually, if you go to a Nintendo event, the Mystery Gift option should automatically show up if you are in the range of the Wonder Spot (the device that gives you the event Pokémon).
• The chances are not perfect, and if your friend didn't visit an event, then it will not likely work and it will say: 'There are no gifts to receive' or so.

P.S. You have to have at least one badge