Originally titled 'Eaters of the Dead', the film went through several re-edits after test audiences did not react well to the initial cut. After re-shooting several key scenes with Michael Crichton taking over as director, the title was changed to 'The 13th Warrior'. The budget, which was originally around $85 million, reportedly soared to more than $110-115 million before principal photography wrapped. With all of the re-shoots and promotional expenses, the total cost of the film was a rumored $160 million.
During the Angel of Death's "recruitment drive", and just after she announces the 13th warrior must not be a Northman, Herger is standing up and looking at Ahmed Ibn Fahdlan. Just few seconds later, Herger is seen sitting down with a different set of clothing.
In the scene where the warriors are outside talking in a circle (just after they have met with the king), you can see one of the warriors with a war hammer resting across his shoulders. The scene shows the hammer end up and the spike end down, but in the next shot the ends are reversed, and then back again.
On the map at the start of the film Baghdad is in the Caucasus between the Black Sea and the Caspian Sea. In reality it is to the south west of there on the Tigris River.