Defeats for Uruguay (3-0 to Bolivia) and Chile (2-0 to Ecuador) ensured Argentina, unbeaten in 27 matches, booked their ticket, leaving just two more automatic spots available in South American qualifying with four matches left.
It caps a fine year for Argentina and Lionel Messi, who won their 15th Copa America in July with a 1-0 final victory over Brazil at Rio de Janeiro's iconic Maracana stadium.
It is also the 13th time in a row that Argentina have qualified for the World Cup having failed to qualify for the 1970 finals in Mexico.
Brazil secured their qualification on Thursday with a 1-0 win over Colombia.
Ecuador look set to join the two continental giants, sitting in third with a six-point gap to the next team and only four matches left to play.
But the fourth automatic qualification spot will go down to the wire with five teams separated by just two points.
Only Venezuela, rock bottom of the 10 team single South American qualifying group, appear out of the running.
Goals from Pervis Estupinan and Moises Caicedo condemned Chile to defeat, and dropped them from fourth to sixth.
They also had Arturo Vidal sent-off in the first half for a high boot.