Karen Hughes will leave her post as counselor to President Bush effective this summer.
Hughes, 45, told reporters Tuesday that she wants to move her family back home to Texas so that she can spend time with her stepdaughter and granddaughter, and start her son, Robert, in high school.
"This is something that my husband and I decided and I went to the president last week and told him it would be better for me and my family to be in Texas," she said.
Hughes said she announced the decision because she had to notify her son's school in Washington, D.C., by May 1 that he will not be returning in the fall, but will complete his last three years of high school in Austin.
Typically in Washington, when someone says they are leaving to spend more time with their family, something else is at work in the decision, including internal strife with colleagues. Hughes said that is not the case this time.
"Let me completely disabuse you of that. This is completely a personal decision," she told Fox News. "In this case, there really is my family. I just think it's right for my family to be rooted in Texas."
It would be true to form for Hughes to leave for family reasons. She has made it practice to depart her senior-level position at the White House each evening at 5:30 in order to get home and be with her family.
That family-first impulse is supported by Bush, who said Tuesday he appreciated the fact that Hughes decided to put her family ahead of her job.
He added, however, that he is not losing his right-hand woman altogether.
"Karen Hughes will be changing her address, but she will still be in my inner circle. I value her judgment, and I will have her judgment. I value her advice; I have her advice. And I value her friendship, and I will have her friendship," Bush said during a photo opportunity with King Mohammed VI of Morocco.
Hughes said she would continue to advise the president from Texas but would not be on the federal payroll. Hughes, one of Bush's closest advisers who directed his communications when the president was governor of Texas, is the first senior-level administration official to leave the high pressure White House.
She said she plans to take a couple weeks of vacation after her departure and then will decide what she wants to do next.
White House Communications Director Dan Bartlett is being considered to replace Hughes as a senior adviser to the president.
Fox News' Carl Cameron contributed to this report.