Baker, Victoria Childress had told the couple, Trina Vodraska and Janelle Sievers, she would not be able to provide them with a cake due to her beliefs.
Childress told TV station KCCI: “They came in, and she introduced herself, I shook her hand and I said, ‘Is this your sister?’”
She said: “I didn’t do the cake because of my convictions for their lifestyle.
“It is my right as a business-owner. And it’s not to discriminate against them.”
Victoria Childress added that the couple were ‘very pleasant’.
The state of Iowa legalised gay marriage in 2009 and prohibits discrimination on the basis of sexual orientation.
Trina Vodraska said: “I appreciated her being honest.” But she further added: “I know Jesus loves me, I didn’t need her to tell me that. I didn’t go there for that, I went there for a cake.”