It had been scheduled to begin in February, but the state mental hospital says it can't complete his mental evaluation until mid-September, nearly two months later than Judge Carlos A. Samour originally planned.
He's holding a hearing Tuesday to reconsider the timing of the trial and other proceedings.
The hospital says the delay is partly because the psychiatrist has to review some of the 40,000 pages of evidence in the case.
Holmes is charged with killing 12 people and injuring 70 on July 20 at an Aurora movie theater.
He has pleaded not guilty by reason of insanity. The trial cannot begin until the sanity evaluation is completed.