The Walking Dead star will play "classic beauty" Emma, who was raised by her father and grandmother, TVLine reports.
The character has enjoyed a privileged life of travelling before arriving at the Ewing's Southfork ranch, where she encounters Ann Ewing (Brenda Strong) - who may or may not be her long-lost mother.
Bell played Amy on the first season of The Walking Dead and has also appeared in such films as 2010's Frozen and 2011's Final Destination 5.
A second season of the new Dallas was confirmed by TNT in June, with the first run premiering to nearly 3m viewers on Channel 5 in the UK last week.
Mitch Pileggi, who plays Ann's scheming ex-husband Harris Ryland, has also been promoted to a series regular for the show's next run.
Dallas continues tonight in the UK at 9pm on Channel 5 and will return to US screens in January 2013.
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> The Walking Dead Q&A: A chat with Emma Bell
Watch the cast of Dallas speak to Digital Spy below: