The 22-year-old initially agreed a switch from Cardiff a fortnight earlier but was recalled by the Blueburds 24 hours later.
But he is now signed up until January 5 and ready to make a debut at Middlesbrough on Saturday.
And he is excited about playing for what he has labelled a ‘big,big club’.
Mason said: “It took a while coming, but sometimes you’ve got to wait for things like this. I am delighted to be here finally.
“I can’t wait to get started – the boys have been on a really good run of late as well so that always helps when you’re coming into a new group, and the lads have been really good to me as well so that’s always nice.
“The manager was trying to sign me for quite a while which is always nice to know and Bolton are a big, big club, especially in this division, so it was a really easy decision for me.
“I have got quite good experience of the Championship and I know a few things in terms of getting out of it too, so hopefully I can put that into my time here at Bolton.”