Casillas has been warming the bench at Real since returning from a broken hand after he fell out with coach Jose Mourinho but Del Bosque said he had faith in his captain, who turned 32 on Monday, and he would be travelling to the warm-up tournament for next year's World Cup.
"We are publishing the squad list in a week's time and as long as nothing strange happens he [Casillas] will be on it because he is our captain who has represented us in recent years and we have confidence in him," Del Bosque, a former Real coach, said at a publicity event in Madrid.
Mourinho's relegation of the hugely popular Casillas to the substitutes' ranks, which he said was for purely sporting reasons, has alienated many Real fans.
Casillas joined the club's academy 23 years ago and has been a fixture between the posts both for Real and Spain for more than a decade.
His list of domestic trophies includes two Champions League crowns, five La Liga titles and one King's Cup and he captained Spain as they became the first nation to win back-to-back European Championships with a World Cup in between.
In his early thirties he should be at the peak of his career but has cut a disconsolate figure in recent months watching from the side of the pitch as Real's La Liga, Champions League and King's Cup campaigns foundered.
"If he had asked my advice I would have told him to do exactly what he has done: be obedient, disciplined and discreet," Del Bosque said.
Casillas's banishment may soon be over as Mourinho appears poised to leave Real after what he himself termed a "disastrous" season and his "worst ever" as a coach.
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