Bildt told reporters in Stockholm that South African jurist Richard Goldstone is a person with "high credibility" and "high integrity" and that his report carries weight.
He said the probe, which alleged that both Israel and Hamas committed war crimes during last winter's Israel offensive against Gaza, is worthy of consideration.
Bildt added the right place for deliberations about the report was the UN human rights council, which is expected to hold an open debate about it on October 14.
Earlier Thursday, Bildt told Swedish Radio that Israel made "a mistake" by not cooperating with the probe, which he called "independent" and "serious."
Sweden currently holds the rotating six-month presidency of the European Union.
Thirteen Israelis and almost 1,400 Palestinians were killed during the Gaza conflict. Israel has rejected the war crimes allegations, declining to cooperate with the probe, fearing bias.