Kerr married British actor Orlando Bloom last month.
"Yes, I am pregnant. Four months along," Kerr told the Spanish edition of Vogue in its September issue.
"I remember on one occasion in the early days (of my pregnancy) when it was still too soon to say anything, and I had a dreadful time at one job," she said, recalling suffering from morning sickness during her first trimester.
The baby's gender was not mentioned in the report.