But despite her extra clothing, she appeared to show off part of her mid-riff while competing in the race.
Fans took to social media to recognise her achievement in taking part in the race.
The sprinter's outfit also drew comparisons to Australian runner Cathy Freeman who won gold in the 400m in Sydney wearing a specially-designed green and white body suit.
Writing on Twitter, Bailey Witt said: 'Feeling so emotional bc (sic) Kariman Abuljadayel is Saudi Arabia's first female sprinter to participate in the Olympics. #feminism #Rio2016'
A user known as A_FarScape added: 'Kariman Abuljadayel is the first. Maybe Saudi Arabia will let more women train and maybe win sprinting events.'
And Sylvester U. Orubele tweeted: 'Karimen Abuljadayel. Well done for even representing!'
The Saudi Olympic Committee lifted a ban on women competing in the Olympics in 2012 despite strong opposition from many quarters of society.
She is one of four women from the Middle Eastern country to compete in the Rio Games alongside Attar, judoka Joud Fahmy, and fencer Lubna Al-Omair, a fencer.
Three of the four women, including Attar, train in the United States using their student status, although Attar is no longer a student.
Today's event was reminiscent of scenes from 2012 when a then-19 Attar was applauded around the 800m track by British fans at the Olympic Stadium.
Attar was born and raised in California and trains at Pepperdine University in Malibu, where she is studying art.
She has dual nationality because of her Saudi father Amer and chose to represent the Middle Eastern country.
But officials demanded that all female competitors would be dressed 'to preserve their dignity' - hence the modest, long-sleeved garments and hijab covering the hair.
It was reported before the London Games that Pepperdine University had been asked to remove photographs from an online biography of Attar because they showed her in a tank top and shorts with no hijab.
In Saudi Arabia, most women cover their heads and faces in public and wear a black cloak called an abaya.
Abuljadayel and Attar are one of a number of Middle Eastern track athletes who have competed in hijabs at the the Olympics, including Noor Hussain Al-Malki of Qatar and Shinoona Salah al-Habsi of Oman.