How many Pokemon are in Pokemon Pearl?

Answer 1

First of all I don't know if I am interpreting what you mean correctly or not, you may be asking how many Pokémon can you catch in total the answer would be 18 boxes, 30 per box plus the 6 in your belt equals 546 total as people who answered before thought or you may mean how many different Pokémon can you catch in Pearl.

With the release of Pearl and Diamond the grand total is 493 different Pokémon.

You can catch most Pokémon in Pearl and Diamond, I don't know the exact number you can catch in Pearl but I will calculate the exact number some time but here is some information that might be of interest, the information may not be 100% complete or accurate but it's based on information I have gathered and as far as I know it is accurate and complete.

Exclusive to Pokémon Pearl

#079 - Slowpoke

#080 - Slowbro

#127 - Pinsir

#199 - Slowking

#200 - Misdreavus

#228 - Houndour

#229 - Houndoom

#234 - Stantler

#363 - Spheal

#364 - Sealeo

#365 - Walrein

#371 - Bagon

#372 - Shelgon

#373 - Salamence

#410 - Sheildon

#411 - Bastiodon

#429 - Mismagius

#431 - Glameow

#432 - Purugly

#484 - Palkia

Exclusive to Pokémon Diamond

#086 - Seel

#087 - Dewgong

#123 - Scyther

#198 - Murkrow

#212 - Scizor

#246 - Larvitar

#247 - Pupitar

#248 - Tyranitar

#261 - Poochyena

#262 - Mightyena

#304 - Aron

#305 - Lairon

#306 - Aggron

#352 - Kecleon

#408 - Cranidos

#409 - Rampardos

#430 - Honchkrow

#434 - Stunky

#435 - Skuntank

#483 - Dialga

Exclusive to Pokémon Ranger

#490 - Manaphy

#489 - Phione (Offspring of Manaphy/Ditto so technically you need Manaphy to get a Phione)

I think there are also Pokémon exclusive to other systems which is a real pain in the butt if the system is out of date.

Pokémon GBA (Game Boy Advance) Extras

Have the GBA cartridge in the Nintendo DS GBA slot while playing Pokémon Diamond or Pearl to find the following Pokémon.

Pokémon Fire Red

#10 - Caterpie @ Route 204 South

#11 - Metapod @ Hakutai Forest

#23 - Ekans @ Route 212 South

#24 - Arbok @ Safari Zone

#58 - Growlithe @ Route 201, 202

#239 - Elekid @ Route 204 South, Powerplant

Pokémon Leaf Green

#13 - Weedle @ Route 204 South

#14 - Kakuna @ Hakutai Forest

#27 - Sandshrew @ Lost Cave

#28 - Sandslash @ Route 228

#37 - Vulpix @ Route 209

#240 - Magby @ Hard Mountain, Route 227

Pokémon Emerald

#204 - Pineco @ Hakutai Forest, Route 203, 204, 229

#207 - Gligar @ Hard Mountain, Route 206, 207, 214, 215, 227

#213 - Shuckle @ Route 224

#216 - Teddiursa @ Route 211, Wisdom Lake

#217 - Ursaring @ Wisdom Lake, Route 216, 217

Pokémon Ruby

#273 - Seedot @ Hakutai Forest, Route 203, Route 204

#274 - Nuzleaf @ Route 229

#303 - Mawile @ Iron Island

#335 - Zangoose @ Route 208

#338 - Solrock @ Thrust Lake, Thrust Lake Surroundings, Wisdom Lake, Aspiration Lake, Tengan Mountain, Departure Springs, Return Cave

Pokémon Sapphire

#270 - Lotad @ Route 203, 204, 205 North, 212 South

#271 - Lombre @ Route 212 South, 229

#302 - Sableye @ Iron Island

#336 - Seviper @ Route 208

#337 - Lunatone @ Thrust Lake, Thrust Lake Surroundings, Wisdom Lake, Aspiration Lake, Tengan Mountain, Departure Springs, Return Cave

Any GBA Pokémon Version

#93 - Haunter @ Forest Mansion

#94 - Gengar @ Forest Mansion Room with eyes

As far as I know the Pokémon below are unobtainable within Pokémon Pearl and Diamond because they are either starter or legendary Pokémon from other versions/consoles or are special event Pokémon and they can only be ontained through migration to Pal Park from GBA Pokémon Leaf Green, Fire Red, Ruby, Sapphire or Emerald or through trades.

Unobtainable within Pokémon Pearl and Diamond.

#001 - Bulbasaur

#002 - Ivysaur

#003 - Venusaur

#004 - Charmander

#005 - Charmeleon

#006 - Charizard

#007 - Squirtle

#008 - Wartortle

#009 - Blastoise

#144 - Articuno

#145 - Zapdos

#146 - Moltres

#150 - Mewtwo

#151 - Mew

#152 - Chikorita

#153 - Bayleef

#154 - Meganium

#155 - Cyndaquil

#156 - Quilava

#157 - Typhlosion

#158 - Totodile

#159 - Croconaw

#160 - Feraligatr

#243 - Raikou

#244 - Entei

#245 - Suicune

#249 - Lugia

#250 - Ho-oh

#251 - Celebi

#252 - Treecko

#253 - Grovyle

#254 - Sceptile

#255 - Torchic

#256 - Combusken

#257 - Blaziken

#258 - Mudkip

#259 - Marshtomp

#260 - Swampert

#377 - Regirock

#378 - Regice

#379 - Registeel

#380 - Latias

#381 - Latios

#382 - Kyogre

#383 - Groudon

#384 - Rayquaza

#385 - Jirachi

#386 - Deoxys

Hope this helps.

Answer 2

493. First is Bulbasaur, last is Arceus. Same goes with Diamond. :)