The New Zealand international was signed by the Californian club on Thursday, having been released by Fulham last May following an injury-plagued two-and-a-half years at Craven Cottage in which he played only 14 times.
Elliott was previously with the Columbus Crew and the Los Angeles Galaxy, with whom he won an MLS Cup title in 2002.
The Earthquakes open their 2009 campaign this Saturday at home to the New England Revolution and San Jose general manager John Doyle believes Elliott will prove to be a valuable addition to the side.
"We have always known that Simon was a quality player," he said. "He had a number of very good seasons in MLS and was able to move to England.
"It has been a pleasant surprise to see him overcome his Achilles' injuries. He once again looks like the Simon Elliott that we have always known."