At age 19 and competing at her first Summer Olympics, Maziah Mahusin was the first female athlete to represent Brunei at the Games. She qualified for the Games through a wildcard place because her best time of one minute and 1.14 seconds, recorded at the Southeast Asian Youth Athletics Championships, was 13.59 seconds slower than the "B" qualifying standard for the women's 400 metres. In an interview with "Reuters" before the Games Mahusin said she felt "deeply honoured" to represent her country and that it was "a dream come true" that she was selected. She felt the inclusion of herself in the Brunei Olympic team would encourage her nation to pursue better standards in sport. Mahusin took part in the contest's sixth heat on 3 August, finishing seventh out of eight runners with a time of 59.28 seconds. Her time established a new Bruneian national record. Overall Mahusin ranked 41st out of 45 athletes. She did not progress into the semi-final after finishing 7.15 seconds slower than the slowest qualifier. Afterwards, Mahusin stated she did not expect to set a new national record having been unwell beforehand but hoped to compete at the Rio Olympics.