They are 21-year-old Newport Gwent Dragons prop Jamie Corsi, 20-year-old Merthyr RFC No 8 Ben Morgan and 21-year-old Tonmawr RFC hooker Rhys Lawrence.
Their two-year deals see them train full-time with Nigel Davies’s professional squad as each also pursues educational or vocational studies.
The first Scarlets development contract went to Llanelli RFC lock Aaron Shingler this season. He took the opportunity to break into the first team, making five Scarlets appearances.
Scarlets Head of Regional Development and Recruitment Gareth Jenkins said said: “Jamie, Ben and Rhys are young men with the potential to be very good players for the region. The full-time training they’ll have with Nigel Davies’s squad means that they have a genuine opportunity to progress to the next stage of their development.
“They will each also be studying for educational or vocational qualifications so that, as well as progressing in rugby, they have an academic or trade base. They will also play a full part in supporting the very busy community programme carried out by the Scarlets – this will involve duties such as visiting schools and coaching children.
“If they progress as we know they can in the next two seasons they will each give themselves a strong chance of becoming a professional in Nigel’s squad.”