"The Olympic family feels the pain of Spanish sport following the death of Yago Lamela, one of the best athletes in our history," wrote the Spanish Olympic Committee on Twitter.
Lamela had retired in 2009 after battling a series of injuries since when he suffered lengthy bouts of depression.
According to Spanish media, his body was discovered at his home in Aviles in the north of the country.
Lamela won the silver medal at the world indoor championships at Maebashi in Japan in 1999 with a new European record of 8.56m before also finishing second at the outdoor world championships in Seville later that year.
On both occasions, he was beaten by Cuban great Ivan Pedroso.
"He was an introverted man but a born competitor. Goodbye to a great athlete," wrote Spanish 20km walking star Paquillo Fernandez on Twitter.