Ryan Dingle and James Hannaford have arrived from National Two South side Launceston, while Jack Martin and Fin Gilding have joined from Western Counties West outfit Devonport Services.
All four approached Saracens about joining, which has delighted coach Stuart Busfield.
The quartet have been training with the club for a few weeks but are now added to the first team squad, which is in need of a boost after a draw and a defeat against title-rivals Totnes and Wessex.
Busfield, who is hoping third-placed Saracens can get their promotion hopes back on track, said: “It is really pleasing to have players of this standard who want to come to our club.
“They certainly bolster the squad and bring some real competition in some positions. Some guys who have been shoe-ins will be feeling some heat now.”
Hannaford has played for Saracens before but went to Newton Abbot and Launceston to play at a higher level. Forward Dingle, who has also played National League rugby for London Irish Wild Geese, has joined Hannaford in moving from Polson Bridge.
“It’s great to be bringing Plymouth talent back to the city from National League rugby,” said Busfield, who team are still in the RFU Junior Vase. “It shows club culture pays dividends.”
Martin and Gilding have made a shorter journey from Services. Both have played in Western Counties West this season and Busfield believes they are a ‘real capture’.
The quartet could make their debut this coming Saturday when Saracens host South Molton.