Juventus claimed the Serie A crown on Sunday as they beat Cagliari 2-0 and Milan crashed 4-2 to Inter in their city derby.
"I'm not used to winning nothing -- it's the first time it's happened to me," he said, perhaps forgetting some of his earlier years in the game, when he won nothing with Swedish side Malmö.
"I'm disappointed. It's a failure."
Technically, 2006 was the last time he failed to win the title as Juventus were stripped of their 2005 and 2006 scudetto crowns due to match-fixing.
However, at the time, Ibrahimovic experienced the thrill of winning as those two titles were only revoked later on.
He feels Milan could have won the title this year had it not been for their well-documented injury problems.
"If we'd had a full squad, we'd have had a better chance of winning," he said.
"Juventus have had a fantastic season and I congratulate them but we gifted them the title a bit because it was in our hands."
Milan had led by four points before a draw and a defeat handed the initiative to Juve, who never let it go.
As for his own future, Ibrahimovic refused to clarify rumours linking him with a move to Real Madrid.
"I want to win and everything depends on what Milan want. I have no doubts about myself but I want to understand what the club wants to do," he said.
"There was a great Milan project. We'll see if they take it forwards. I hope they do."
That could be taken as a warning to Milan that he may opt to leave if they cannot match his ambition.
Despite winning winning three titles with Inter, two with Ajax and one each with Milan and Barcelona, Ibrahimovic has never won the Champions League.