The Scarlets have a number of injuries at loose head and the 21-year-old, originally from Tredegar, will remain West Wales Region until 31st December 2016.
Garrett, who has represented Wales U20s in the Junior World Championships in 2015, made his debut for the Men of Gwent during Judgement Day in April 2015 against Scarlets. He also played his part in the Newport Gwent Dragons’ Premiership Select side during last seasons British and Irish Cup campaign.
Dragons Head Coach, Kingsley Jones commented: “We are happy to cooperate with the Scarlets and assist them in their current situation.
“This is a fantastic opportunity for Luke to gain experience and accelerate his development by gaining some invaluable experience in the Guinness PRO12 and potentially European competitions.
He continued: “The Dragons are well served at loose head with new signings Sam Hobbs and Tom Davies available, plus Phil Price is due to return from injury shortly. However, should an issue arise there is a facility to recall Luke to the Dragons squad.”