The new contract will keep the 21-year-old at the Suns until the end of the 2029 season.
Essendon had been leading the pursuit for the key forward, with Geelong, Collingwood and Hawthorn among other rivals interested.
Gold Coast had reportedly tabled a five-year, $5 million offer to counter massive interest.
Walter described the club as his home after re-signing and is one of 17 Suns academy products on their AFL list, joined by the likes of Bodhi and Zeke Uwland.
"I'm stoked to have signed on for a further three years with the club," Walter said in a club statement.
"Having grown up on the Gold Coast, been part of the academy and now playing at AFL level for the Suns, the Gold Coast is home and there's nowhere else I would rather play.
"I'm excited for what the future holds on the Gold Coast.
"The recent results haven't been what we've desired, but what we're building here at the Suns is something I'm really looking forward to continue playing a role in."
In his third season since being drafted with pick No.3 in 2023, Walter has kicked a career-best 23 goals across 12 games as the 14th-placed Suns (7-10) struggle to recapture last year's form.
Gold Coast are also aiming to land the signatures of fellow Suns forwards Jamarra Ugle-Hagan and Ben King.
Coach Damien Hardwick has been adamant that 2020 No.1 pick Ugle-Hagan was a "long-termer", while King - set to become a free agent - is also weighing up interest from interstate clubs.
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