The Castle Fire is a part of a larger wildfire now known as the SQF Complex Fire. It has burned more than 90,000 acres and forced evacuations and road closures in the South Valley.
Many staff members have been evacuated from the area and park managers say they are closing all entrances to protect visitors and resources.
The announcement for the closure of Sequoia was made on Monday, and that for Kings Canyon was made on Thursday.
The Giant Forest and sequoia trees will be inaccessible to visitors, park officials said.