My alternator went out on my 2003 es300. I decided to try and save 150$ by going to a 'pull a part' location instead of autozone for a replacement. I pulled an alternator out of a 2003 Toyota Camry because there aren't any similar lexus' at the lot. I assumed it was interchangeable parts for those cars. It seems however that the alternator doesn't quite fit in my Es300. Are these alternators different between these cars? If they are, which Lexus/Toyota vehicles have the same alternator as a 2003 es300?

I would assume its engine dependent.

'03 L4 Camry Alternator
2AZ - Toyota Part No: 27060-0H010
RockAuto Results

'03 V6 Camry Alternator
1MZ - Toyota Part No: 27060-0A070-84
RockAuto Results

'03 ES300 Alternator
1MZ - Lexus Part No: 27060-20230
3MZ - Lexus Part No: 27060-20270
RockAuto Results

So, what did I gather from this research? I'm not sure. I'm wholly confused now lol.

According to RockAuto and other aftermarket part sources, the 1MZ Camry's alternator works with the 1MZ ES300's alternator.
(I'm going to assume the 3MZ listing for the alternator is for the 2004 model year ES300.)
According to Lexus/Toyota part sites, they are different parts.

I think your best bet is to find V6 Camry's to take an alternator from.
Likely, the Camry you pulled from was the L4, which has a different, less powerful alternator.
If it truly was a V6 Camry, then I've got no idea.

Good luck.

​​​​​​Thanks, very helpful. I probably did take it out of the L4.

EDIT: I just looked up the car by its VIN we found on the pull a part website and it is an L4.

Upgrade to a higher output RX330 or Highlander alternator while your at it.

I did not know they were compatible. Good to know for the future. The alternator I ended up going with, before I saw this reply, was from a wrecked 02 es300. Maybe if this one doesn't last I'll opt for the higher output option.
Thanks