how many pokemon can you catch in the game pokemon diamond with out trades?

Yeah..U can trade your poke from Leaf Green, Fire Red, Emerald, Ruby, Sapphire, Pokemon Ranger (Poke Ranger only Manaphy egg that U can trade) but not from Red, Blue, Yellow, Gold, Silver, Crystal, Pokemon Mystery Dungeon, ...

U practically can get most of poke in Diamond without trading, but some are required trading...The following poke that required trading:

-all starters from Kanto to Hoenn (1st to 3rd generation) such as Bulbasaur, Ivysaur, Venusaur, Charmander, Charmeleon, Charizard, Squirtle, Wartortle, Blastoise, Chikorita, Bayleef, Meganium, Cyndaquil, Quilava, Typhlosion, Totodile, Croconaw, Ferraligatr, Treecko, Grovyle, Sceptile, Torchic, Combusken, Blaziken, Mudkip, Marshtomp, Swampert

-the starters in Diamond that U don't choose so if U choose Chimchar as your starter, U need to trade to get Turtwig, Grotle, Torterra, Piplup, Prinplup, Empoleon

-legendaries from 1st to 3rd Generation:

Articuno, Zapdos, Moltres, Mewtwo, Mew, Entei, Raikou, Suicune, Ho-Oh, Lugia, Celebi, Latias, Latios, Kyogre, Groudon, Rayquaza, Regirock, Registeel, Regice, Jirachi, Deoxys

-To unlock Regigigas, U need to have the other 3 Regi so in other words, U gotta trade those 3 Regi first, then U can face Regigigas...

-all poke that evolve by trading:

Alakazam, Machamp, Golem, Gengar, Slowking, Politoed, Kingdra, Scizor, Electivire, Magmortar, Porygon-2, Porygon-Z, Huntail, Gorebyss, Rhyperior, Dusknoir

-the one and only non-starter and non-legendary poke that needs trading from Emerald/Ruby/Sapphire coz Nintendo missing this poke: Tropius

-since you play Diamond, U need trading for all poke that exclusive to Pearl version such as:

Slowpoke, Slowbro, Pinsir, Misdreavus, Mismagius, Houndoom, Houndour, Stantler, Spheal, Sealeo, Walrein, Bagon, Shelgon, Salamence, Shieldon, Bastiodon, Glameow, Purugly, and the one and only legendary exclusive to Pearl and it appears in Pearl front cover: Palkia

Yeah..it looks so much so let's count:

-starters from 1st to 3rd Generation: 27

-starters in Diamond that U don't choose: 6

-legendary from 1st to 3rd Generation: 21

-Regigigas: 1

-Poke evolve by trading: 16

-Tropius: 1

-exclusive to Pearl: 19

Sum of 'em is: 91 poke

Total poke in PokeDex: 493 poke

So, poke that U can catch in game is 493-91=402 but since Darkrai, Shaymin, Arceus event hasn't come out so U only can get 402-3=399 poke in total...

Have U gotten 399 already?

Additional Details:

To get Manaphy, U don't have to trade from Pokemon Ranger..U can get from Toys R' Us Event in Sept 29, 2007 and U can also get it from Nintendo World Store Event...so I don't include Manaphy and its breeding child, Phione in the list of poke that needs trading...Also if U live in Japan or U go to Japan to get Darkrai, U can get poke up to 400 without trading...The US Darkrai Event will comin' soon..Don't miss it

yes its possible, ranger all u can do is get manaphy, collesm no, u dont trade from other games but u do transfer them ( need 2 see all pokemon 1rst) the go to pal park and have the other game in the gba slot and u transfer a pokemon 2 the pal park and catch em dont worry its easy 2 catch them really really easy vote me 4 best anser!!!!

493

Over 400.