Boe, who will perform in Dublin and Belfast next weekend with Michael Ball, had been married for 16 years to Sarah, and the couple have two young children.
It was reported that he'd got involved with another woman. In an exclusive interview, Alfie tells Shuffle that he was in a dark place at the time: "I found that I lost myself a little bit, I got very depressed, I missed home dreadfully and I couldn't see a way out of the state I was in."
Although he doesn't blame the pressure of his career for the split with his former wife, Boe says it did play a part as it involved spending long periods away from home.
"I think the time apart did sort of distance us a little bit and we tried to make things work as far as being together. They [Sarah and their two children] came over to visit me, but inevitably I was still working, having to do interviews and so on, and I couldn't focus 100 per cent on the family when they were around.
"It did have an impact, but now I have to look at it as a life lesson to know where the faults are, know where the pitfalls are, know what to avoid in the future, know how to be a better person, know how to protect myself and just try and move forward in this industry a little bit."
However, Alfie had to work through the pain of losing his wife before coming to terms with his new life.
"I was devastated, but when I look at it on the bigger picture you have to sort of assess and realise that everything happens for a reason and if the reason for the breakdown of my marriage was to become a better person then I'm sort of accepting of that, even though it was something I didn't want to go through," he says.
"I still have a lot of love and affection for my ex-wife. She's an absolutely amazing woman and a wonderful mother, and I'm grateful for the years that we had together, I really am. It was a blessing for me to have met her and to have her in my life, and we're still best friends. To have the children that we have together, I wouldn't change a thing."
Alfie says he co-wrote "60 or 70 songs" during lockdown, mostly about the turmoil in his personal life - and plans to release an album next year.
"It was really sort of therapeutic," he says of the songwriting. "It was a self-development sort of thing, assessing myself as a person, so I was grateful for the opportunity without really realising what it was doing to me."
And then you have your other 'wife', Michael Ball, how is that going?
"Oh well, that's a rocky road as well," Alfie laughs. "Michael, bless him, he's a great guy. It's not very often that you get to work with a partner in the industry that you really, really connect with, and you really get on well with and you respect each other.
"It's been so exciting working with the guy from day one, building that relationship on stage and off stage as well. He's a really good guy, and he's very supportive."
Boe's family on his mother's side are from Mornington, Co Meath, where he still has cousins. "I'm sure I'll get the call for tickets to the shows," he laughs. "I love the Irish audience. Everybody goes crazy. They are always up for a good night."
Ball and Boe play Dublin's 3Arena on December 6 and Belfast's SSE Arena on December 7.