Del Bosque led Spain to World Cup victory in 2010, when they beat the Netherlands 1-0 in South Africa.
"Argentina are a tough team to play against - a real nuisance, if I may use the word - and they know exactly what they need to do," del Bosque told the El Pais newspaper in an interview published on Saturday.
Del Bosque pointed to Argentina's comeback victory over England as evidence of their quality.
"I see the final as favouring Spain, but they need to be wary of the Argentines, given how difficult they are to face and their experience," he said.
The 75-year-old also praised Spain's performances at the tournament and backed them to lift the trophy.
"In the matches we have watched, the game was played exactly on the national team's terms; they dominated the situation and demonstrated both assurance and confidence," he added.
The World Cup final between Spain and Argentina will be played at the New York New Jersey Stadium on Sunday.
FIFA World Cup 2026 final
The 2026 FIFA World Cup final took place at MetLife Stadium in New Jersey on Sunday, July 19th, with Spain edging out defending champions Argentina for football's biggest prize.
Match report from final | Full World Cup schedule & results | Knockout bracket | Past winners of the tournament