On a brisk afternoon at the Cardiff International Sports Campus, Jack Concannon netted the only goal of the game with a superb finish just before half-time.
Cardiff had the first sight on goal within the opening three minutes when a ball over the top found Gary Madine.
But the experienced striker's half-volleyed attempt was well-blocked by centre-half Joe Redmond who deflected it behind for a corner.
Having withstood some early pressure from the hosts, Blues began to find their feet, although they were struggling to find a way past a well-organised Cardiff back line.
Blues were not far away with their first attempt of the game in the 21st minute.
Concannon did well to use his pace to get in down the left before dragging the ball back for Caolan Boyd-Munce, who saw his low goalbound shot deflected behind for a corner.
From the resultant corner Blues forced the ball into the back of the net, but it was ruled out by the referee for a foul on Ben Margetson during the build-up.
Moments later Blues 'keeper Moha Ramos did well to deny Madine from close range.
Blues were beginning to put together some neat passing moves in the middle of the pitch and it was from one of these that they fashioned their next chance, but Kane Thompson-Sommers' low shot flew just wide of the far post.
Cardiff were still posing a threat themselves and they twice went close within the space of a minute.
Shamar Moore fired over the bar, before Ramos did well to palm Will Vaulks' powerfully hit effort over the bar.
The game began to ebb and flow and Boyd-Munce did well with a shot from the edge of the area which was turned behind for a corner, before Joe Redmond had his strike cleared off the line by Jake Evans.
But Blues didn't have to wait too much longer to open their account through Concannon, and what a finish it was.
The midfielder drove on into the box, before taking the ball around several defenders and then curling a peach of shot into the top corner.
Half-time: Cardiff City Under-23s 0 Blues Under-23s 1
Blues made a decent start to the second period of the game and with 52 minutes on the clock Concannon's pass found Thompson-Sommers, but he shot straight at Hall in the Cardiff goal.
Seconds later the Cardiff stopper was called into action again as Miguel Fernandez fizzed in a shot from the edge of the box, but Hall was equal to it.
Cardiff were inches away from levelling on the hour mark as a long throw from the left reached Madine.
But the Cardiff number nine headed the ball down and just inches wide of the upright, with Ramos well beaten.
On 62 minutes, Blues made their first substitution with Jayden Reid replacing Fernandez and then five minutes later George Baker entered the contest in place of Ben Forrest.
Reid was soon into the thick of the action. Andrews laid the ball off to him on the right side of the area, and he tried his luck with a sidefooted effort, but Hall denied him with a low diving save
Cardiff were increasingly to long balls from their own 'keeper, but the Blues defence was continuing to stand strong.
Blues very nearly doubled their lead on 78 when Concannon struck the post and then Andrews headed over from a corner.
But it was the post at the other end that came to Blues' rescue minutes later as Cardiff captain Vaulks saw his shot cannon back off the upright
Cardiff threw men forward in the final minutes, but were ultimately unable to find a way back, ;leaving Blues to return to the Second City with a deserved win.
Blues: Ramos, Forrest (Baker, 67), Redmond, Roberts, Burke, Stirk, Thompson-Sommers (Campbell, 86), Boyd-Munce, Concannon, Fernandez (Reid, 62), Andrews.
Subs (not used): Bradley-Hurst.
Goals: Concannon (42).