Daly, who turns 24 on Monday, joins the Bank of Scotland Premier League club on a two-and-a-half-year deal.
'I've been monitoring the player for a couple of months but first saw him around two years ago when he was with Stockport,' manager Craig Levein told the club's website.
'It's no secret that we've been thin on the ground in the striker department and, additionally, Jon gives us something different to what we already have.
'Jon has scored nine goals this season already and although he's been signed essentially as a target man, he is certainly capable of adding to this tally.'
Daly joins an already sizeable Irish contingent currently playing in the Scottish Premier League.