Having rejected offers from Newcastle Jets and Adelaide United, the 33-year-old Irishman will join Williams and former Olyroos keeper Jack Duncan in the Kingdom.
Relegated from the top-tier of the Saudi Pro League last season, Al-Qadsiah have been on the lookout for a proven marksman to spearhead their promotion push when the new season commences on August 16.
And Williams, who played alongside Keogh for a season at Glory, put his name forward to club officials as a possible answer to the conundrum.
Keogh’s two-year deal will be activated once he goes through the formality of a medical.
Despite signing a one-year contract extension in March, Keogh’s Glory future always looked clouded once the club had nailed down marquee forward Bruno Fornaroli, and coach Tony Popovic made it clear in recent weeks he did not figure in his plans for the new season.
The ex-Republic of Ireland international bagged 15 goals in 2018-2019 as Glory romped to the Premier’s Plate.
Having signed for Perth in 2014, he was Glory’s most prolific scorer in the A-League era with 55 goals from 122 appearances.
Williams, who was part of the Socceroos squad for last month’s 1-0 friendly loss to Korea Republic, told The World Game last month of his desire to help the club bounce back.
“I’ve still got two more years here - I’m settled here and so is my family,” he said.
“It was a tough season last year. I was trying to drag the boys through it and be a leader of the team but it wasn’t meant to be.
“Everything happens for a reason. Both Jack and I were part of the mess - as every player was - and it’s up to us to pull ourselves out of it.”
Speaking of his move, Keogh told Back Page Football: “I wanted to see out my playing days at Perth Glory but unfortunately things haven’t worked out this offseason and I have been given a great opportunity in Saudi Arabia.
“I don’t want to play for another club in the A-League or have to sit out a season due to being out of favour,” he said.
“Of course I would be open to a return to Glory in the future, I’ve loved playing here in front of the fans and my aim was always to leave a legacy.”
