Spurs forward Johnson completes Palace switch
The Wales international, 24, has signed a four-and-a-half-year deal at Selhurst Park.
The forward, who fell out of favour under Thomas Frank at Spurs despite being the London club's top scorer last season, is set to make his debut for Palace in their Premier League match against Newcastle at St James' Park on Sunday.
"I'm really excited and I'm really happy," said Johnson, who is Palace's record signing. "Crystal Palace are such a great club, one that I've always admired.
"It's a great time for me to be here and join the journey that this club is on."
Palace manager Oliver Glasner said: "Brennan will give us options in our attacking play with his pace and goalscoring ability."
Johnson finished with 18 goals last season and scored the winner in the Europa League final against Manchester United to end Tottenham's 17-year wait for silverware.
However, he has largely been a back-up to Mohammed Kudus since Frank replaced Ange Postecoglou.
The transfer will be a huge boost to Glasner, who said his threadbare side were in "survival mode" following Thursday's 1-1 draw with Fulham.
FA Cup holders Palace, 10th in the Premier League table, travel to Newcastle eager to end a six-match winless run in all competitions.