The top-seeded Nadal beat Argentine lucky-loser Alund 6-3, 6-7 (2-7), 6-1 in one of the day's semifinals at Sao Paolo.
The Spanish former world No. 1 advanced to the title round last week at Vina del Mar, where he was upset by Argentina's Horacio Zeballos.
The two South American events were the first appearances for Nadal since his return from a seven-month layoff due to a knee injury.
Nalbandian cruised to a 6-3, 7-5 victory over Italian Simone Bolelli in Saturday's other semifinal.
The Argentine fired 11 aces and went 5-for-5 on break points.