Cardiff looked strong for the first 20 minutes with flowing attacks involving tight passing but they could not hit the back of the net even when the ball fell to Peter Thorne just outside the area - his right-footed half volley rocketed over Dean Delaney's crossbar.
The Bluebirds broke the deadlock in the 35th minute when Graham Kavanagh's free kick on the left curled into a crowded Vale area. Gavin Gordon scored the goal, bundling the ball over the line with his knee to Delaney's right.
Cardiff nearly added to their tally twice in the 45th minute. Kavanagh's 30-yard free kick bounced back off Delaney's right post and Scott Young volleyed onto the crossbar from another Kavanagh corner.
The Valiants eventually began to get into the game after the break and in the 61st minute Marc Bridge-Wilkinson's 20-yard effort flew just past Neil Alexander's right-hand post.
However, Lennie Lawrence's men put the game out of Vale's reach in the 65th minute when they scored their second.
A devastating corner by Kavanagh found Thorne leaping above his markers to nod the ball into Delaney's bottom left-hand corner from six yards.
Gutted Port Vale manager Brian Horton said after the game: "I thought we gave them too much respect in the first half and we've conceded two goals from set pieces again.
"I don't think we get our fair share of good referees especially when you're down here. We've got to turn it around quickly."