Trainers in Pokemon Brilliant Diamond and Shining Pearl can obtain Jirachi as long as they have save data from another game.
There are quite a few special bonus rewards for dedicated trainers in the new Pokemon Sinnoh region remakes, Brilliant Diamond and Shining Pearl. These primarily include mythical Pokemon that require a bit of outside work to obtain. Fortunately, when it comes to Jirachi the Wish Maker, some fans may have already completed the necessary steps.
How to Get Jirachi in Pokemon Brilliant Diamond and Shining Pearl
Players can add Jirachi to their team by taking a trip to Floaroma Town and speaking with the elderly gentleman in town. He can be found with an elderly lady in the wildflower field to the immediate left of the town's southern entrance.
Floaroma Town will be available to players once they receive their first Gym badge from Oreburgh City Gym Leader, Roark. This will give them the ability to use Hidden Move: Rock Smash to remove boulders blocking the path to the town. Trainers can reach Floaroma Town from Jubilife City via Route 204, to the north.
An elderly couple will be standing in the wildflower field to the immediate left once the player enters the town. Speaking to the man will prompt him to hand over Jirachi, the steel and psychic-type "Wish" Pokemon. It joins the team at level 5.
Note that the older gentleman will only give the trainer a Jirachi if they have save data from Pokemon Sword and/or Shield on their Nintendo Switch.
Other available legendary Pokemon in Brilliant Diamond and Shining Pearl include Manaphy and Mew.