In USA, Linda is played by Caroline Rhea.
In case you're not from the USA, here are some of the other actors:
Linda Flynn-Fletcher is played by Caroline Rhea.
Vincent Martella plays Phineas and Thomas Sangster plays Ferb.
There Mom says Phineas is in Switzerland and Ferb is at Camp David.
Ferb is Phineas's stepbrother. Phineas's mom married Ferbs dad.
Allison Stoner plays Isabella's voice in Phineas and Ferb.
Ferb is Phineas' step brother and the Dad's real son. Phineas and Candace are the Mom's real kids and the Mom and Dad got married when all the kids were small. The dad's side of the family is from England and are in a couple of episodes and the mom's parents are in a couple too. The mom's parents are in the episode were they go camping.
Carolin Rhea
Vincent Martella plays Phineas and Thomas Sangster plays Ferb.
Maulik Pancholy plays Baljeet on Phineas and Ferb.
Mitchell Musso plays jeremy on Phineas and ferb!
There Mom says Phineas is in Switzerland and Ferb is at Camp David.
Me
Caroline Rhea
Allyson Stoner voices Isabella on Phineas and Ferb.
Ferb is Phineas's stepbrother. Phineas's mom married Ferbs dad.
Phineas is voiced by Vincent Martella.
Ferb is from the Dad. Phineas and Candace are from the Mom.
Allison Stoner plays Isabella's voice in Phineas and Ferb.