The Perth-born stage star will play the role of Elle Woods, made famous by Reese Witherspoon in the 2001 movie, in the upcoming Australian version of the Broadway hit.
She will be joined by her fellow Wicked star and Young Talent Time host Rob Mills, who plays Elle's fickle boyfriend Warner.
Emerging love interest Emmett will be played by David Harris, who Durack also performed alongside in Mamma Mia.
Fashion model and TV host Erika Heynatz will make her theatre debut in the role of Brooke, while Cameron Daddo returns to the Australian stage for the first time in 20 years as Professor Callahan.
Durack said reprising a stage relationship alongside old friends Mills and Harris comes with equal advantages and drawbacks.
"I think it's going to give us a really good place to start from as we don't have to work out how to work together," she said.
"(That said) I'm extremely professional except for when I'm on stage with Rob Mills and David Harris.
"They're the only people in the industry who can make me laugh so I think we're going to have to be professional and rein that in."
Mills paid tribute to the talents of Durack and her growing profile in Australian musical theatre following two consecutive major leads.
But the actor will not be letting up in larrikin attempts to sabotage the slick running of her high energy performance.
"Our relationship is great and I'm really looking forward to working with Lucy again," he said.
"This time I don't have as much to do so I think I'll have a bit more fun and mess around a bit and try and make her laugh more."
The casting was announced on Monday by producer John Frost who praised the calibre of the show's leads.
* Legally Blonde will have its Australian premiere at the Sydney Lyric Theatre on October 4, 2012.