The 25-year-old 'It's My Party' singer put on a spectacular show during the music festival and looked like she just came off a catwalk as she strutted her stuff across the stage.
Jessie looked fierce as she posed in the customised suit by designer Hasan Hejazi, which featured a body leotard underneath a sheer mesh catsuit, with tuxedo stripes on the legs and arms.
Jessie, who has just returned from Rio de Janeiro, Brazil where she performed at the Rock in Rio festival, appeared on stage in a white cape, but it wasn't before long she whipped it off and belted out her powerhouse vocals.
The former The Voice UK coach, performed tracks from her new album Alive and was joined on stage by US songstress Brandy, as well as British MC Dizziee Rascal.
She also performed a selection of her chart-topping hits including 'Price Tag', 'Nobody's Perfect' and 'Laserlight'.
Fans took to Twitter to praise Jessie's vocal talents. One fan said: "@jessiej #itunesfestival beautiful performance! Took my breath away," while another commented: "@JessieJ you blew me away last night @itunesfestival you were incredible thank you!"
After her showcase, Jessie took to Twitter to sum up her emotions on the night.
She said: "So overwhelmed right now. Partying with my closest people! Thank you iTunes, thank you everyone who gave me love tonight. My heart is heavy with love! #Alive."
The iTunes Festival continue's tonight (24 September) with Robin Thicke. Justin Timberlake and Katy Perry are also scheduled to perform later this month.
Download the free official iTunes Festival app to see the line-up, apply for tickets, and watch the shows live or on repeat for a limited time. Visit: www.itunesfestival.com.
Watch a clip of Jessie J performing 'It's My Party' below: