The singer floored fans in a statement black patterned mini dress punctuated by bold red roses.
The dress featured a flattering off-the-shoulder silhouette with voluminous ruffle detailing - teamed with strappy heels and Alesha's gorgeous long dark hair.
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Sharing a GIF of herself in the piece on Instagram, Alesha wrote: "This is your 1 hour warning! Semi final no.5! @bgt tonight on @itv and @wearestv1 8pm!"
Needless to say, fans were obsessed with Alesha's latest dress. One wrote: "Oooo I can't wait to see this beautiful outfit!" Another added: "Love your dress!"
Alesha's dress was stunning!
Last week, Alesha took to the judging panel in a striking black dress that featured show-stopping puffed sleeves.
Pairing her fabulous off-the-shoulder look with dangling earrings that reminded us of chandeliers, and with her hair pulled back into a sleek ponytail, the star proved yet again that she's one of the best-dressed celebrities around.
That is one statement sleeve!
Alesha has been killing it in recent weeks with her eye-popping outfits, and the beautiful yellow mini dress that the singer wore on the third semi-final might just be one of the most fabulous frocks we've seen all year long.
Alesha's dress wowed fans on the third semi-final
Featuring black detailing running along the low-cut sweetheart neckline, the famous mum finished off her ensemble with plenty of gold jewellery, some strappy heels and plenty of body highlighter for a glowing look.
To welcome back the series after lockdown in September, Alesha dazzled in a gorgeous rainbow-hued dress from Rami Kadi, commanding attention in the strapless sequinned number.
Alesha wore this dazzling design for the return of BGT
But even more spectacular was the doting mum's eye-popping jewellery!
The TV favourite completed her look with a few choice Veiled Rebel pieces, proudly showing her support to a black-owned brand in the midst of the Black Lives Matter movement.
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