The 26-year-old missed out along with Denny Landzaat and Sander Boschker when Van Basten named his final 23-man side for the tournament.
"I would have liked to play at Euro 2008, but the understanding was clear," the Chelsea player told NOS Langs de Lijn.
The defender, who finished the season on loan at Sevilla, was a late addition to Holland's pre-tournament training camp because of injuries to fellow defenders Andre Ooijer and Mario Melchiot.
And Boulahrouz, who himself only recently returned to action after a long period out with a groin injury, revealed he was always going to make way if his rivals proved their fitness.
He added: "From day one that was what we agreed on. It is tough for me, but I must accept it.
"Van Basten gave me the chance to prove myself, I am grateful for that. Out of the blue he selected me. In that short time I showed that I was ready for Euro 2008, but you don't make agreements for nothing."