Hollyoaks stars were full of praise for Rachel, who wrote the film and played social worker Joanne.
The British actress accepted her award with both speech and sign language, which she said was her way of fulfilling a promise to the short's 6-year-old star Maisie Sly.
In her acceptance speech, Shenton said: "This is happening".
Standing alongside fiance Chris Overton, Rachel then told the crowd: "Our movie is about a deaf child being born into a world of silence".
"Deafness is a silent disability, it is not life threatening and you can not see it so I want to say the biggest thank you to the Academy for allowing us to put this in front of a mainstream audience".
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Maisie didn't go up on stage to collect the award, but Overton told BBC 5 live: "When we won I could see her up there jumping up and down and that was surreal".
She had never acted before but Shenton said Sly had "taken it all in her stride".
Rachel is one of just a few actresses to give their Oscars acceptance speeches in sign language.
Rachel wrote, produced and starred in the film about childhood deafness after she became passionate about the issue when her father became deaf when she was young. She is an ambassador for the National Deaf Children's Society and climbed Mount Kilimanjaro in 2013 in aid of the charity.
Overton also thanked their parents for making cup cakes to raise funds for the film, and those who backed its crowdfunding campaign.
She was among those who congratulated Rachel on her win, tweeting: "YAYAYAY!"