The budding star, coached by Kaiser Chiefs front man Ricky Wilson, beat off stiff competition from Lucy O'Byrne to take the crown.
The 29-year-old, from Alva in Clackmannanshire, had been the bookies' favourite to win the final.
After his victory was announced, Stevie said: "I never thought this was possible."
His debut single - a cover of Lost Stars - has already been released.
He has also been asked to perform at this year's T in the Park.
The firefighter only ended up on the show after his workmates entered him.
Asked what colleagues at his fire station would think, he said: "I think they're over the moon for me because they all wanted me to go for it.
"A lot of people have saw something in me that I didn't see, and even standing up there I've still got that self-doubt and I think it's going to take a while to click in, to take in, that I've actually won The Voice 2015."
A spokesman for bookmakers Coral said: "Stevie has proved a popular winner in this year's series of The Voice as he was well backed to win the show ever since his blind audition.
"All three previous winners of The Voice have struggled in the charts but our odds suggest Stevie could have some success with his debut single and album."
Ricky Wilson said Stevie had won by simply singing the song and "connecting with people".
He added: "Stevie's a typical Scotsman. Although on paper he was the favourite all along, he still felt like the massive underdog."
You can watch Stevie's winning performance on The Voice here.
Scottish firefighter Stevie McCrorie has won the grand final of the BBC show, The Voice.