The deal is a two-year contract worth nearly $5 million, according to sources close to the situation.
Golden State general manager Larry Riley says the team has been interested in adding the well-traveled Amundson for several weeks, and that he adds key depth to the Warriors' frontcourt. Amundson could provide a key rebounding presence inside that the team has lacked, too.
The Hornets had been pursuing Amundson hard to join the recently acquired Trevor Ariza as a key newcomer, with new general manager Dell Demps flying to Los Angeles in August to lobby the former Phoenix banger face-to-face and present him with a Hornets jersey.
But with the Hornets still possessing roster spots left to fill with only 11 players under contract and thanks to a $1.25 million performance bonus Hornets center Emeka Okafor is expected to trigger in his contract by season's end, New Orleans couldn't start Amundson's contract at higher than roughly $1.9 million without straying into luxury-tax territory.
That enabled the Warriors, still possessing their $2.1 million bi-annual exception and with $2.4 million left from their mid-level exception, to make an offer starting at higher than $2 million and outbid the Hornets.
The Warriors, Hornets and Indiana Pacers had moved to the forefront of the Amundson bidding last month, but sources close to the process said that the 27-year-old wanted to give teams such as New Orleans and Indiana more time to see if they could potentially make a roster move that would lead to a more lucrative offer before telling the Warriors he was accepting.
The Pacers coveted Amundson as a potential replacement for the recently traded Troy Murphy, but Indiana didn't have roster room with a league-maximum 15 players under contract.
The fact that Amundson lasted this long on the open market ranks as one of the late-summer surprises of this chaotic NBA offseason. With his high-energy contributions throughout Phoenix's unexpected run to the Western Conference finals last season, Amundson had Suns management privately concerned for much of last season that he would receive a long-term offer much earlier in free agency.
As one of the faces synonymous with the Suns' vaunted bench unit, Amundson became a fan favorite in Phoenix despite his offensive limitations and modest averages of 4.7 points and 4.4 rebounds last season.
Although Amundson didn't hide the fact that he initially hoped to stay with the Suns, Phoenix moved on early after Amare Stoudemire bolted for the New York Knicks, filling its Amare void by re-signing Channing Frye, signing Hakim Warrick and trading for Hedo Turkoglu to be a ball-handling power forward.
Marc Stein is a senior NBA writer for ESPN.com. Information from The Associated Press was used in this report.