Signed earlier in the summer from RB Leipzig after playing a central role in Spain's Euro 2024 triumph, Olmo had to wait two games until Barca could register him due to LaLiga's strict financial control rules.
But Olmo said it was worth the wait, as his return to the club where he spent seven years in the youth academy before joining Dinamo Zagreb aged 16 was better than expected.
"I've been looking forward to my debut since for a long time and it couldn't have been in a better way," Olmo told DAZN on Tuesday.
"It's been many years since Barcelona won here, it's such a tough place to play so the end result is just unparalleled.
"I've felt very good, I was really looking forward to it. Today it finally happened, I'm very happy to have helped the team and even better to have scored. I'm delighted."
Barcelona top the standings on nine points from three games, two ahead second-placed Villarreal. They next host Real Valladolid on Saturday.
