The 27-year-old, who had a similar spell with Surrey last season, could feature in five County Championship matches during his month's stay.
Notts have plenty of pace bowling cover, but boss Mick Newell insists all will be required over the season.
"Luke is very much a part of that and by playing some competitive cricket, he'll return more prepared to play in the first team," he said.
Fletcher, who has taken 213 career first-class wickets, said: "It's an opportunity to play some four-day games, take wickets, hopefully contribute to victories for Derbyshire and ultimately push my case to find a way back into the Nottinghamshire team.
"It's an ideal loan move because, particularly after recently becoming a dad for the first time, it means I can still be based mostly at home rather than a completely different part of the country."
Nottinghamshire seam bowler Luke Fletcher has joined Derbyshire on loan.