The towering 20-year-old was released from Auchenhowie at the end of last season, having spent time on loan at Cowdenbeath during the most recent campaign.
But after his spell at Rangers ended, Hogarth has been snapped up by the skybet Championship side, and Academy coach Andy Reid spoke of his delight.
"Nicky has good experience around the first team with Rangers so it's a really good addition for us.
"A lot of work has gone into the recruitment and we're delighted to get it over the line.
"He's a player we have a lot of hope for. He's got a real presence, a great stature and a really mature head on his shoulders," he told the Forest website.
Hogarth landed the SPFL reserve league title with Rangers in season 2018-19 alongside team-mates including Nathan Patterson and Kai Kennedy and also spent time on loan at East Stirlingshire and Stirling Albion – one of his father’s former clubs.
Dad Myles is also a goalkeeper, currently on the books as a player and coach at Linlithgow Rose – and the glove genes run in the family.
Nicky’s move south means he leaves behind younger brother Jay, who is also at Rangers and has recently been training with the first-team goalkeepers since the Premiership champions returned for pre-season.
Nottingham Forest is also home to ex-Rangers defender Joe Worrall and Scotland international Scott McKenna as well as former SPFL players Tyler Blackett, Lyle Taylor and Fouad Bachirou.