"For several reasons, this seems like a good time to pass on the privilege of representing the 21st District to someone else," Smith, who has served in Congress since 1987, said in a statement. "I have one new grandchild and a second arriving soon!! And I hope to find other ways to stay involved in politics."
Smith leads the House Committee on Science, Space and Technology, and also serves on both the judiciary committee and the homeland security committee.
Smith joins a growing list of Republicans not seeking a re-election, including Reps. Pat Tiberi of Ohio, John J. Duncan Jr. of Tennessee, Dave Reichert of Washington, Charlie Dent of Pennsylvania and Rep. Dave Trott of Michigan.
He made headlines earlier this year when he asked Americans to get their news directly from President Donald Trump.
"The national liberal media won't print that, or air it or post it," Smith said in January
. "Better to get your news directly from the President. In fact, it might be the only way to get the unvarnished truth."
His seat is considered safely Republican, though Democratic Army veteran Joseph Kopser is running for the position.
With the announcement of fellow Texas Republicans deciding to retire, Rep. Pete Sessions made it clear he is planning to stick around the House.
"I have busted my ass to get a million two in the bank," Sessions said off the House floor on Thursday, apparently referencing his campaign war chest. "I enjoy this more than anybody knows."
He said the departures of Smith, along with Rep. Jeb Hensarling, who also announced recently he would retire
after this term, would alter the Texas delegation.
"They've done an awesome job for us," Sessions said. "The legacy of a couple of these guys ... is going to be missed. I think their distinction among their colleagues is well-noted."
Rep. Sam Johnson, former prisoner of war in Vietnam along with Sen. John McCain and another Texas Republican, is also not running for re-election in 2018.
This story has been updated to include additional developments.