The squeaky clean star has said his fellow Disney Channel stars - who are both three years younger than him - pressured him into smoking a joint when they were teenagers.
Joe, 24, told Vulture magazine: ''The first time I smoked weed was with Demi and Miley. I must have been 17 or 18. They kept saying, 'Try it! Try it!' so I gave it a shot, and it was all right. I don't even smoke weed that often anymore.''
The singer also opened up about his rocky relationship with Demi, claiming the 'X Factor' USA judge - who went to rehab for ''physical and emotional issues'' in 2010 - was actually struggling with full-blown ''drug abuse'' and he only stayed with her because he wanted to help her.
Joe recalled: ''I really got to know her and got to see the ins and outs of what she was struggling with, like drug abuse. I felt like I needed to take care of her, but at the same time I was living a lie, because I wasn't happy but felt like I had to stay in it for her, because she needed help.
''I couldn't express any of that, of course, because I had a brand to protect.''
Joe - who also dated Taylor Swift as well as Demi - joked he was glad he waited for the right girl and not his ''bats**t crazy'' ex.
In the revealing Q&A, he said: ''I lost my virginity when I was 20. I did other stuff before then, but I was sexually active at 20. I'm glad I waited for the right person, because you look back and you go, ''That girl was bats**t crazy. I'm glad I didn't go there.'''
Joe's band - also formed of his two brothers Nick and Kevin - split in October.
Steven Tyler prays for Chris Cornell during Asia show.
'Pirates of the Caribbean' is an exciting new career development for Brenton Thwaites.
The actor didn't want to be "wolfy".
Tragedy strikes in Manchester