2021 Challenger de Buenos Aires

Country	Player	Rank1	Seed
BRA	Thiago Monteiro	92	1
ARG	Juan Manuel Cerúndolo	103	2
ARG	Francisco Cerúndolo	110	3
PER	Juan Pablo Varillas	127	4
BOL	Hugo Dellien	128	5
BRA	Thiago Seyboth Wild	129	6
ARG	Sebastián Báez	140	7
ARG	Tomás Martín Etcheverry	144	8

• ¹ Rankings are as of 4 October 2021.^[2]

The following players received wildcards into the singles main draw:

• Román Andrés Burruchaga
• Mariano Navone
• Juan Bautista Torres

The following players received entry from the qualifying draw:

• Francisco Comesaña
• Martín Cuevas
• Carlos Gómez-Herrera
• Ignacio Monzón

• Sebastián Báez def. Thiago Monteiro 6–4, 6–0.

• Luciano Darderi / Juan Bautista Torres def. Hernán Casanova / Santiago Rodríguez Taverna 7–6^(7–5), 7–6^(12–10).