|Isabelle and Sahara Roberts As Sydney DiMera|
|Days of our Lives|
|Portrayed by|| Avery and Cade Seger (2009)|
Hailey and Lauren Sinnema (2009–10)
Elizabeth and Mariam Tovey (2010–11)
Isabelle and Sahara Roberts (2011–12)
Nadia and Talia Hartounian (2013–14)
Berlyn and Brooklyn Baca (2014)
|Current status||Former; Recurring|
|First appearance||January 28, 2009|
|Last appearance||October 30, 2014|
|Created by||Dena Higley and Christopher Whitesell|
|Introduced by||Ken Corday and Gary Tomlin|
|Fullname||Sydney Anne DiMera|
|Born||January 28, 2009|
|Residence||Los Angeles, CA|
|Elizabeth & Miriam Tovey As Sydney DiMera|
Sydney Anne DiMera is the daughter and second and youngest child of EJ DiMera and Sami Brady. Sydney is born in secret on January 28, 2009, while her mother is in witness protection, and she is switched shortly after birth with the daughter of a teenage mother, Mia, who has agreed to give her baby up for adoption to Nicole Walker. Nicole, who has miscarried her fiancé EJ's daughter, has arranged in secret to adopt Mia's baby and pass the child off as EJ's, fearful that she would lose EJ without a baby.
When Nicole learns that Sami had just recently given birth to her and EJ's daughter the same day Mia gave birth to hers, Nicole switches the babies, preferring to have EJ's biological daughter over an unrelated child. Nicole instantly bonds with Sydney, and vows to always protect her no matter what happens. Sami and EJ are none the wiser to Nicole's treachery, and Sami and Rafe bond with "Sami's" daughter, while EJ and Nicole bond with "their" daughter.
EJ eventually learns that Nicole had a miscarriage and he kicks Nicole and Sydney out of the mansion, not knowing the truth about Sydney. Eventually, Sami also learns that Sydney is her biological daughter. Soon after, EJ learns that Sydney is his biological child with Sami. However, the family reunion turns into a nightmare when Brady Black bails Nicole out of jail and she kidnaps Sydney. Nicole has a change of heart and decides to tell EJ and Sami where Sydney is, but she is knocked out by Anna DiMera, who takes Sydney. It is later revealed that Anna was hired by EJ to kidnap Sydney.
Sydney becomes the subject of many custody battles between EJ and Sami over the next few years, with Nicole involved, as well, during the time she is married to EJ. They later come to an agreement, though, and Sydney is able to stay with her entire family, including her siblings, Johnny, Allie Horton and Will Horton. Sydney became an aunt when Gabi gave birth to Arianna Horton, Will's daughter.