The actor took to Instagram on Monday to share the special news that he popped the question to his lady love, Kate Austin, while on vacation in Italy, and she said yes!
"Something extra romantic happened in Italy last night," Greene wrote alongside a series of snapshots that showed the fancy new sparkler. "I am very excited to share my engagement to the most gorgeous woman (inside and out) that I have ever met. beyond thrilled to begin this next chapter together."
Speaking exclusively with ET's Deidre Behar, Greene opened up about his new fiancee and the special moment he asked her to be his wife.
According to Greene, he fell for Austin when he first saw a photo of her, before they even met, and he asked a mutual friend to introduce him.
"[I] messaged her right away and asked if she wanted to go to a movie," Greene recalled. "All within an hour [of seeing her photo.]"
"I wrote a song about the moment and our love," he added, referring to the romantic tune "I Love Now" off his new album, Freedom for Your Soul.
When asked how he knew Austin was the one for him, the actor got romantically poetic, sharing, "We are like two puzzle pieces that just fit perfectly together in every way."
Additionally, Greene says that Austin gets along really well with his son, Oliver, from a previous marriage, which also played a role in his decision to pop the question.
"She just keeps getting more amazing as time goes on," Greene shared. "As does our love and connection."
As for the proposal itself, Greene said he had been waiting for days for the exact right moment to come along.
"I had been carrying the ring in my pocket the whole first week we were in Italy waiting for that magical moment," he recalled. Ultimately, he waited until they'd made their way to a small, ancient city of Matera, in Southern Italy, where it "felt like no one else was there but us."
"It was very planned and also spontaneous and I simply got down on one knee and asked her to marry me," Greene shared. "She has this infectious giggle and laugh that can light up a whole ancient city, and that was her reaction with a resounding 'Yes!'"
As for the impressive engagement ring, Greene revealed that the whole thing is vintage and as historically resonant at the 9000-year-old city he waited to propose in.
"The ring is a vintage 1920’s Art Deco from Paris," he said. "It was inspired by and around the time they discovered Tutankhamun's tomb in Egypt. The [shape of] the side of the ring resembles the pyramid steps."
"I had a dear friend who deals in vintage rings do a sneaky shopping trip for me with Kate," he continued. "So I knew she loved it, but she didn’t know that I knew."
Greene also opened up a bit about the wedding he and Austin are thinking about having, explaining that they would "both prefer it to be intimate and possibly a destination," but that those conversations haven't really begun.
"Even though we’ve been together for four years, we’ve never discussed it once!" Greene said. "So it's all new. It will probably be quite small and very romantic. Simple and delicious."
Since they don't know exactly what the size and scope of the ceremony will be, Greene explained that he's not sure how many of his When Calls the Heart co-stars he'd be inviting, but he hopes he'll get a chance to welcome quite a few.
"We haven’t decided how big or small to make it, but I’d love to invite the whole cast. And also former co-stars who I am very close too, like Candace Cameron Bure and Danica McKellar, but it just depends on how intimate we go."