Jelimo had a promising start for the 2012 season finishing second behind Malika Akkaoui of Morocco in an indoor meeting at Lievin, France, running a Kenyan indoor record of 1:59.10 seconds. Her indoor season was crowned by gold medal at the 2012 World Indoor Championships in Istanbul, Turkey, improving her time to 1:58.83 seconds. She was almost a second ahead of the silver medallist Nataliia Lupu of Ukraine.