The 21-year-old singer and actress said on Wednesday's episode of the Smallzy's Surgery radio show that she encouraged the Game of Thrones star to date Jonas.
"Oh yeah," she said when asked if she takes credit for the pairing. "I did get that text from Sophie saying, 'So tell me about Joe.' I was like, 'Go for it!'"
Turner and Jonas were first linked in October 2016, and announced their engagement the following October.
"I actually just saw them both for the first time since they got engaged," Steinfeld said. "I'm freaking out about it."
Steinfeld is close pals with Turner, and collaborated with Jonas and his band, DNCE, on the single "Rock Bottom." Steinfeld and Turner became friends after working together on the 2015 movie Barely Lethal.
"When I met Hailee, she like ran over and gave me the biggest hug and said, 'I'm so excited to work with you!' And I was like okay, I'm going to get along with her," Turner said in a 2015 interview with Who What Wear.
Steinfeld released her debut EP, Haiz, in November 2015, and will next star in the Transformers spinoff Bumblebee: The Movie.