The actress said she is reprising her role as Donna Martin in the CW show, which also sees Jennie Garth return as Kelly Taylor.
She told People: "Donna was such a huge part of my life. It's going to be so fun to work with Jennie again and see where Donna is today.
"When they say you can't go home again, it's not true. I'm headed back to the zip code I know best and couldn't be happier!"
Spelling stayed with the original series throughout its ten-year run, during which her character married high school boyfriend David Silver (Brian Austin Green).
She added: "Donna loved designing and wanted a career in fashion. It'll be fun to explore that storyline. And I'm sure fans will be dying to know if she's still married to David!"
90210 also stars Rob Estes, Lori Loughlin, Shenae Grimes, Tristan Wilds and Jessica Walter.
> Priestley keen to star in '90210' spinoff