She stepped out in a burgundy brocade dress by Michael Kors, paired with a black cardigan and pointed kitten heels.
And it's not the first time Michelle has worn the designer frock, having worked it twice before at high-profile events.
She showcased the shift-style number first at a White House Christmas party in 2009 and again, teamed with a flower brooch, to the Medal of Honour ceremony in November 2010.
Barack and Michelle's daughters, Malia and Sasha, looked to be following in their mother's footsteps last night as they wowed in jewel-toned A-line skirts.
Malia opted for a blue design with a simple black tee while Sasha chose a green printed skirt and a bow-detail blouse.
Obama tweeted his delight at being elected for a second term and shared a touching photo of himself with Michelle.
He also honoured his wife in a heartfelt speech, saying: "I have never loved you more, I have never been prouder to watch the rest of America fall in love with you, too, as the nation's First Lady."
Aww, here's to another four years of fashionable outfits!
What do you think of Michelle's dress? Let us know in the comments below.
Read more: Katy Perry takes her adorable grandma to meet President Barack Obama
Read more: Barack Obama: Jay Z asked me for parenting tips