Goalkeeper Valdes replaces Villarreal's Diego Lopez as Spain's third-choice behind number one and captain Iker Casillas of Real Madrid and number two Pepe Reina of Liverpool.
In the forward line, Pedro is included along with Bilbao's Fernando Llorente, while Fenerbahce's Daniel Guiza and Sevilla's Alvaro Negredo miss out. Martinez was preferred to Marcos Senna and Santi Cazorla, both of Villarreal.
"We assessed the players' form over the balance of the season and we need to take the best players regardless of age," Del Bosque said at a news conference.
"We are guided by the head but the heart also helped," he added. "I know that missing out on a World Cup is a real blow."
The 22-year-old from Santa Cruz de Tenerife bagged 12 in the league, four in the Champions League, three in the King's Cup, two at the Club World Cup, one in the European Super Cup and one in the Spanish Super Cup.
"It's great news and I'll be with a team mate which is very positive for Athletic Bilbao," Martinez said on the club's website.
"I can't really explain what it means yet but of course I never expected the good fortune that I have had."
Among the European champions' injury concerns, Liverpool striker Fernando Torres and Arsenal captain Cesc Fabregas were in the squad as expected and Del Bosque said their prognosis was positive.
"We still have some slight concerns but they have been included because the message we are getting from the medical staff is positive and they are expected to arrive at the championships at 100 percent," he said.
