Barrios, born in Buenos Aires to a Paraguayan mother, was picked to reinforce a forward section deprived of key striker Salvador Cabanas, recovering from being shot in the head in a Mexico City bar argument in January.
The 25-year-old Barrios, with 18 goals in the Bundesliga this season, is not the only Argentine-born player on the list named by coach Gerardo Martino, also an Argentine.
Midfielders Jonathan Santana of VfL Wolfsburg and Nestor Ortigoza, who plays for Argentinos Juniors in the country of his birth, are also naturalised Paraguayans.
"It's clear there's no discussion about his (Barrios's) footballing qualities. The days we're going to spend together will be good for him to get to know the rest of the lads and get into the group," Martino said.
"On the basis of what we see we'll take a final decision," he told a news conference regarding Barrios's chances of making it into Paraguay's definitive squad of 23 at the end of May.
Paraguay will prepare for the South Africa finals at a training camp in Evian les Bains in France and play several warm-up games in Europe from the second half of May to early June.
They meet holders Italy, Slovakia and New Zealand in group F at the finals starting on June 11.
Squad:
Goalkeepers: Justo Villar (Real Valladolid), Aldo Bobadilla (Independiente Medellin), Diego Barreto (Cerro Porteno)
Defenders: Denis Caniza (Leon), Paulo Da Silva (Sunderland), Claudio Morel (Boca Juniors), Julio Cesar Caceres (Atletico Mineiro), Carlos Bonet, Julio Manzur (both Olimpia), Dario Veron (Pumas UNAM), Aureliano Torres (San Lorenzo), Antolin Alcaraz (Club Bruges), Marcos Caceres (Racing Club)
Midfielders: Edgar Barreto (Atalanta), Cristian Riveros (Cruz Azul), Osvaldo Martinez (Monterrey), Jonathan Santana (VfL Wolfsburg), Victor Caceres (Libertad), Enrique Vera (LDU Quito), Sergio Aquino (Libertad), Eduardo Ledesma (Lanus), Nestor Ortigoza (Argentinos Juniors)
Forwards: Marcelo Estigarribia, Jorge Achucarro (both Newell's Old Boys), Roque Santa Cruz (Manchester City), Nelson Haedo Valdez, Lucas Barrios (both Borussia Dortmund), Oscar Cardozo (Benfica), Edgar Benitez (Pachuca), Rodolfo Gamarra (Libertad)
