She ran at the 2008 IAAF World Indoor Championships but did not reach the final after a poor showing in the semifinal. Montsho reached her first world final at the 2008 Beijing Olympics, but her time of 51.18 left her in last position. The following year, she ran 49.89 in the semifinals at the 2009 World Championships in Athletics which was enough to make the final round of the 400 m. She ran slower in the final than she did in the semis and finished last as a result. She ended the year with a fifth-place finish at the 2009 IAAF World Athletics Final.