Waratahs' McKellar rules out becoming next Wallabies coach
New Zealand's Schmidt announced in February that he will stand down after Australia's Bledisloe Cup clash with the All Blacks on October 4 in Perth to spend more time with his family.
McKellar has been touted as a potential candidate to become Australia's fifth coach in six years, after Michael Cheika, Dave Rennie, Eddie Jones and Schmidt.
However, he said he was not interested.
"I'm not in the mix for the Wallabies gig," he told reporters as he prepared the 'Tahs for a clash with Super Rugby table-toppers Waikato Chiefs in Sydney on Friday.
"I came back to help rugby in this country by helping New South Wales and the Waratahs.
"I'm loving the challenge, loving the players and staff. We've got a tremendous facility and I'm enjoying life in Sydney.
"That's my job, and I've signed here for three years," he said.
McKellar only joined the club this season after a stint with English Premiership giants Leicester, which followed a successful spell with the ACT Brumbies.
Removing himself from the conversation has left the Queensland Reds' Les Kiss as a frontrunner.
Kiss is contracted to the Reds until the end of next year but Rugby Australia chief Phil Waugh indicated on Wednesday he was open to the idea of a Wallabies coach also holding a Super Rugby job.
"We're going to get to the best possible outcome. And if that includes shared services, job-share kind of things, then we'll do that," Waugh said.
Schmidt will lead the Wallabies against the British and Irish Lions in June-July-August and the subsequent Rugby Championship before quitting.
The new coach will lead them to the 2027 World Cup, which Australia will host.