The German departs Tyneside after a difficult first season with the Magpies, where he scored eight goals in 33 Premier League games but struggled in the second half of the campaign.
Juventus will reportedly pay a £3.5 million loan fee, and have added Woltemade to their Deadline Day signings alongside Tottenham midfielder Pape Matar Sarr.
"Newcastle United forward Nick Woltemade has completed a season-long loan move to Serie A side Juventus," the club said in a statement.
"The German international has featured 53 times in all competitions, scoring 11 goals, since joining the Magpies from VfB Stuttgart last summer.
"Everybody at Newcastle United wishes Nick the very best of luck for the season ahead."
Woltemade could make his Juventus debut against AC Milan on Sunday, September 6th.