Vlasic's deal is worth a reported $56 million over the eight years, while Jones' deal is worth $5.75 million per year.
"We're thrilled we could get this extension done early and ensure one of the league's top defensemen will remain in San Jose for the long term," Sharks general manager Doug Wilson said in a statement of Vlasic.
"Marc-Edouard has been an integral part of this team, both on and off the ice, and we are excited to have him in San Jose for at least the next eight years."
Vlasic, 30, finished second on the Sharks in 2016-17 in average time on ice per game (21:14), and ranked second among team defensemen in points (28), goals (six), assists (22), shots on goal (144) and game-winning goals (two).
His 146 blocked shots ranked second on the team, as did his 2:04 of shorthanded time on ice per game.
Having played his entire career in San Jose, Vlasic owns 254 points (53 goals, 201 assists) in 812 regular-season games. In addition, he has 29 points (three goals, 26 assists) in 114 playoff games.
The 6-foot-1, 205-pound native of Montreal was selected by San Jose in the second round (35th overall) of the 2005 NHL draft.
Jones posted a 35-23-6 record, including two shutouts, in 65 games last season with a .912 save percentage and 2.40 goals-against average. His wins ranked seven and his .958 shorthanded save percentage ranked 14th among NHL goaltenders.
"We're very happy we could get this extension done with Martin and feel that he is just beginning to hit his peak in terms of growth and prime playing seasons," Wilson said.
"He has proven that he is more than capable of excelling in high-pressure situations and big games, and we feel he has become one of the top goaltenders in the League. He is a calming influence in net for our team and we're excited to have him in net for us for the foreseeable future."
The goaltender was selected to his first NHL All-Star Game during the 2016-17 season.
Since joining the Sharks, Jones leads the NHL in games started (130) and is tied for second in wins (72) among all league goalies. In addition, his 2.33 goals-against average ranks 13th in the NHL. He finished tied for seventh in voting for the NHL's Vezina Trophy, awarded to the league's top goaltender.
Jones helped backstop San Jose to its first Stanley Cup Final appearance in 2016, setting single playoff franchise records for games played (24) and wins (14). He won the Stanley Cup during the 2013-14 season as a member of the Los Angeles Kings.
The 6-4, 190-pound native of North Vancouver, British Columbia, was signed by Los Angeles as a free agent on Oct. 2, 2008. He was acquired by San Jose from Boston on June 30, 2015.