The 28-year-old London Welsh player replaces Felipe Contepomi, who is not included in coach Santiago Phelan's second-string squad after the Pumas' 2-0 defeat in their series against England.
There are six changes from the team that lost the second Test to England 51-26 last weekend, four in the backs and two, plus one positional switch, in the forwards.
Half-backs Tomas Cubelli and Benjamin Madero come in for Nicolas Vergallo and Contepomi while Tomas Carrio replaces the injured Manuel Montero on the right wing and Matias Orlando comes in for centre Gabriel Ascarate.
Tomas de la Vega comes into the back row with Tomas Leonardi dropping down to the bench and Benjamin Macome moving from flanker to number eight. In the second row, Esteban Lozada replaces Julio Farias Cabello who is also out of the squad.
Contepomi, Vergallo, Farias Cabello and Tiesi could be in line for places Phelan will add to his 30-man first-choice squad for the southern hemisphere Rugby Championship later in the year.
It will be Argentina's third meeting with Georgia after two victories at World Cups.
"We know there's a lot to improve. We really didn't play well in either match against England," Phelan said.
"We improved our attitude in the second Test and we must maintain it for this match. We want to improve in defence because we gave away seven tries in the last match," he added.
"Georgia are a hard team, very direct in their game so contact will be very important... They have quality players who play (club rugby) in France."
Team: 15-Martin Bustos Moyano, 14-Belisario Agulla, 13-Matias Orlando, 12-Gonzalo Tiesi (captain), 11-Tomas Carrio, 10-Benjamin Madero, 9-Tomas Cubelli; 8-Benjamin Macome, 7-Tomas de la Vega, 6-Rodrigo Baez, 5-Mariano Galarza, 4-Esteban Lozada, 3-Maximiliano Bustos, 2-Martin Garcia Veiga, 1-Guillermo Roan
Replacements: 16- Mauricio Guidone, 17-Bruno Postiglioni, 18- Francisco Gomez Kodela, 19-Tomas Vallejos, 20-Tomas Leonardi, 21-Martin Landajo, 22-Benjamin Urdapilleta, 23-Gabriel Ascarate
- Sports & Recreation
- Felipe Contepomi
- Santiago Phelan
- Benjamin Madero
- Nicolas Vergallo
- Benjamin Macome