|First Appearance||Big Sister Dora|
|Relatives||Dora (sister), Guillermo (twin brother), Elena (mother), Cole (father), Valerie (grandmother), Diego, Daisy and Alicia (cousins)|
|Voiced By|| Olivia Coronel (Dora the Explorer)|
Breanna Lakatos (Dora and Friends)
Isabella Márquez is Dora's baby sister. She is a 1 year old pacifier baby and is the twin sister of Guillermo. She appeared in several episodes of Dora the Explorer which that some episodes that she doesn't appear. She is seen sucking on her pacifier and sleeps with him everyday but in a separate bed. She wears a pink shirt, a white diaper, and a pink bow on her brown hair. She appeared in Dora the Explorer games on NickJr.com and appears to also have super powers in the episode, "Super Babies". Like Guillermo, she remained unnamed until the episode "Dora's Jack-in-the-Box", where her name was revealed. She also appeared in the Dora And Friends episode "Magic Land" in which she was a little older and could actually speak in full sentences. She is voiced by Breanna Lakatos.
- In Dora and Friends: Into the City!, a slightly older Isabella lives with her twin brother, big sister, parents and Abuela in the city of Playa Verde.