While pre-race favourites Brenda Jepchirchir and Beatrice Chepkoech were chasing the first sub-30-minute 10km on African soil, Cherop stunned the field by claiming victory in 30:43.
She finished ahead of Jepchirchir, who clocked 30:52, while Chepkoech settled for third in 31:52.
Cherop told SABC Sport that winning the sold-out race in Durban was an unexpected bonus.
" I did not expect it, but my target was to come third. I am so happy to win here today. I did not expect to win. The weather was good so I am happy," said Cherop
The 23-year-old says the race started at a blistering pace, forcing her to run much faster than she had planned.
She explained that the leading group was covering the distance at around 2:55 per kilometre, leaving her with no option but to stay with them if she wanted to remain in contention.
Cherop, who also competes in the half-marathon, admits she never thought she would overtake Jepchirchir, who had been tipped as the favourite.
Her target before the race was simply to run around 31 minutes, but everything came together perfectly as she pulled off one of the biggest upsets of the day.
Despite beating her fellow Kenyan, Cherop says she has great respect for Jepchirchir.
She believes the race favourite pushed the pace too hard in the opening 5km and paid the price in the closing stages, allowing her to take advantage and secure the victory.