Cohen, D-Tenn., said in a statement he was "stunned and dismayed" by the result, Politico reported Thursday.
The test on Victoria Brink, 24, was done with Cohen's participation and paid for by CNN.
"I still love Victoria, hold dear the time I have shared with her and hope to continue to be part of her life," Cohen said.
The congressman said he found out about Brink three years ago during an Internet search.
"I Googled her mother, found out she had a child and the math looked pretty accurate," Cohen said earlier this year. "The mom told me we had a lot of catching up to do."
Texas oilman John Brink, who raised the woman, is her biological father, the test found.