The standard was so high that Brazil's Darlan Romani was left in fourth, despite having three throws over 22m. It was the first time in world championship history that more than one man had gone past 22m in the final.
Kovacs' throw was the third equal best in history, and the best since 1990 when American Randy Barnes set the world mark.
Kovac's last throw was the only time he went over 22m on the night. The giant athletes hugged each other after the event, in celebration of the amazing contest.
"I didn't lay a further enough gauntlet down with the first throw," said Walsh. "I was bang on with all the rest, exactly what I was supposed to be doing, but didn't quite nail one out there a bit further. But I gave myself a good go at it.
"Really happy that I did that, my best comp all year as in attacking every throw and nailing the intent, but there's a bit of a bitter taste in the mouth with not getting the gold.
"There was an amazing atmosphere out there. There has been a lot said this week about the lack of crowds but that was not the case tonight.
"I do the sport to be challenged and to challenge myself. I went into the last throw walking towards that, looking forward to it, and believing I had what I needed.
"I didn't quite do it but I gave it a good nudge.
Aucklander Jacko Gill finished seventh, his throw of 21.45m just short of his personal best.
Barnes holds the shot put world record with a mammoth 23.12m throw in Los Angeles in May 1990. But shortly afterwards he was banned for two years for using an anabolic steroid. He was reinstated and won the 1996 Olympic gold but received a lifetime ban two years later.
Asked when Barnes' 1990 record would be beaten, Walsh said: "Like a few other records out there are controversial ones. People say Joe's (winner Joe Kovacs) got the clean world record now…I personally don't look at it that way.
"The world record is in a book and it's 23.12m. Yes, there may be some controversial things around that, but that is the mark I'm looking to beat."
