An Amadou Bakayoko goal proved in vain as the Saddlers were dumped out of the FA Cup by League Two Newport.
Frank Nouble’s deflected 18th-minute strike put the Exiles ahead and Shawn McCoulsky made it 2-0 straight after the restart.
Substitute Bakayoko pulled one back but it wasn’t enough.
The tie’s first attempt fell to the hosts after eight minutes, Matty Dolan seeing a half-volley strike his own man and ricochet out of play.
It was from a deflection that the Welsh club – currently eighth in League Two – went ahead ten minutes later.
Nouble bundled his way past Adam Chambers and Shaun Donnellan before unleashing a powerful left-footed shot which took a wicked deflection off Jon Guthrie and looped into the top corner.
The Saddlers enjoyed plenty of possession during the first half but struggled to penetrate a well-organised, deep-lying Exiles defence.
Tyler Roberts’ half-volley was well blocked by Ben White, with Erhun Oztumer collecting the loose ball and firing over from 25 yards.
A training ground routine saw Zeli Ismail deliver a corner along the ground to Roberts, making a run across the near post, but the striker steered his first-time effort high and wide.
Michael Flynn’s men had a chance to double their lead on the stroke of half-time when Nouble bulleted a header wide from Robbie Willmott’s in-swinging corner.
But Newport did make it 2-0 within 30 seconds of the resumption, McCoulsky latching onto White’s incisive pass and placing a low right-footed shot across Mark Gillespie and into the far corner.
The second half followed a similar pattern to the first, with Walsall seeing plenty of the ball but failing to trouble Joe Day in the home goal.
The Exiles could have put the game to bed on 75 minutes as Matty Dolan’s near-post corner was glanced narrowly wide by Nouble.
And the hosts were made to pay for that miss as the Saddlers pulled one back three minutes later.
Second-half substitutes Maz Kouhyar and Amadou Bakayoko combined to devastating effect, the former crossing for the latter to glance a fine header just inside the far post.
Kouhyar then fired over from 25 yards as the visitors threw the kitchen sink in search of an equaliser, but County held on to reach round two.
Team: Gillespie, Kinsella, Guthrie, Donnellan, Leahy, Ismail, Chambers, Edwards, Morris (Bakayoko 62’), Oztumer (Kouhyar 74’), T Roberts.
Subs not used: L Roberts, K Roberts, Devlin, Flanagan, Jackson.
Attendance: 2,701 (399 Walsall supporters).