Casemiro played alongside the defender in Brazil's friendly draw with Panama on Saturday, with the South American side held to a 1-1 draw by the Concacaf nation.
Lucas Paqueta scored to put the Brazilians in front, but Adolfo Machado 's strike saw Panama earn a shock draw as Brazil struggled without the likes of Neymar and Vinícius Junior in the team to spark the attack.
But Casemiro was still full of praise for Militao and claims the 21-year-old will be a welcome addition for the Spanish giants.
"I've got to congratulate Real Madrid for signing him because half of Europe wanted him," he said, via AS.
"Militao has earned the right to play at the best club in the world and he'll be very welcome next season."
Militao is in just his first campaign at Porto after making a switch from Sao Paulo in August last year.
Militao is the first addition made during Zinedine Zidane’s second reign in the Spanish capital, with the Frenchman having moved quickly to land a top target upon returning to Real.
For Militao, there is also still work to do for Porto, who are set to face off with Liverpool in a Champions League quarter-final tie and are tied atop their domestic league with Benfica.
But Casemiro is sure his Brazil team-mate will remain locked on his performances ahead of his move to Spain.
"He's with Porto, they're playing in several competitions and I'm sure he's focused on Porto,” he said.