Wynaut was introduced in Pokémon’s third generation as the pre-evolved form of Wobbuffet, and you’ll have to acquire one if you want to fill out Pokémon Brilliant Diamond and Shining Pearl’s National Pokédex. However, this Pokémon cannot be caught in the wild in either Brilliant Diamond or Shining Pearl; the only way to get a Wynaut is by breeding its evolved form, Wobbuffet.
Before you can breed for a Wynaut, you’ll need to first unlock the National Pokédex, as neither Wynaut nor Wobbuffet are part of the Sinnoh region’s Pokédex. Next, you’ll need to acquire a Wobbuffet, which you can find by using the PokéRadar at either Lake Valor, Lake Verity, or Lake Acuity. You can also find one wandering around the Dazzling Cave or Stargleam Cavern hideaways in the Grand Underground. We’d recommend checking out the Grand Underground hideaways, as you can also catch a Ditto there, which makes the whole breeding process a lot easier. Lastly, you’ll need the Lax Incense, which can be found on Route 225 behind a small tree that can be cut down.
After fulfilling the above prerequisites, equip your Wobbuffet with the Lax Incense, which allows the Pokémon to lay Wynaut eggs. Attempting to breed Wobbuffets without one holding this item will only yield more Wobbuffets. Now, head over to the Pokémon Nursery in Solaceon Town, and drop your Wobbuffet off alongside either a Wobbuffet of the opposite gender, or a Ditto, which is able to breed with any Pokémon regardless of its gender. Eventually, the two Pokémon will produce an egg that will hatch a Wynaut. You can use the Egg Monitor Pokétch app to see when the egg is ready for pickup.