Video and photos of the heartwarming gesture show Cynthia DeBoutinkhar hugging the protester outside the Noor Islamic Cultural Centre in Columbus, Ohio, on Saturday.
The lone protester, identified only as Annie, had signed up for the Global Rally for Humanity, a social media campaign that reportedly organised protests at dozens of mosques and Islamic centres across the US and the world.
However her one-person protest quickly turned into a multi-way dialogue with counter protesters outside the mosque.
"If you're Muslim, we can't be friends," she told Micah David Naziri, who was captured on video approaching the woman to start a conversation. "My Bible says that."
However Annie was welcomed by Mr Naziri and other counter-protesters, who spoke with her for over 40 minutes about her fears and concerns regarding the religion.
It was then that Ms DeBoutinkhar approached Annie with open arms and asked if she could give her a hug.
"Something came over me and I went up to her and asked if I could give her a hug. I wouldn't let go of the hug,” Ms DeBoutinkhar later wrote on her Facebook page.
“I felt her body go from tense to soft and I asked her to please come inside with me. She was actually AFRAID! I asked if I look scary to her. She said I didn't. I promised her I'd stay right by her side the whole time."
"When we walked in, me carrying one of her two signs, everyone was waiting for her in the lobby. We all began applauding. I stayed by her side as I promised."
Annie was then given a tour and spoke with mosque leaders for nearly two hours before leaving with a copy of the Quran.
“Will Annie ever become Muslim? ” Ms DeBoutinkhar questioned on Facebook.
“Who knows. That's in God's hands. But her parting words for me were this: ‘You were all really nice. I don't approve of the violence or killings (neither do we), but I'll read this book. I had no idea Muslims could be nice to me, even after I stood out there with those signs. Sorry."
She noted that Annie left the mosque without her signs.