Leeds began brightly and went very close to bagging a brilliant opener when Luis Sinisterra's crossfield pass was headed on by Luke Ayling to Willy Gnonto who fired a vicious volley just wide.
But Ayling was pushing very high up the pitch from right back and Cardiff went ahead with a break down that side in the 23rd minute which ended with Josh Bowler netting at the second attempt from a Callum O'Dowda cross.
Leeds looked to rally but it was a similar story with chances either not created or not taken and Cardiff doubled their lead in the 39th minute but this time with an attack down the other side.
This time Bowler was able to get in behind Leo Hjelde after a one-two and the Bluebirds eventually worked the ball to Ike Ugbo who got in behind Ayling to net at the far post after an initial Aaron Ramsey shot was blocked.
The start of the second half mirrored the pattern of the first with Leeds on top but this time the Whites pulled a goal back through a bullet header from captain Liam Cooper to convert a Summerville corner in the 49th minute. Cooper injured himself in the process and was stretchered off but Daniel Farke’s side continued to dominate but without being able to find the back of the net.
The Whites looked to be heading for an opening weekend defeat but Summerville changed that in the 95th minute when reacting quickest to a Sinisterra shot that was blocked to rifle home a first time attempt into the bottom left corner to send Elland Road wild. Leeds United writer Lee Sobot hands out the scores from a dramatic afternoon at Elland Road.
1. Illan Meslier
6 - Two goals conceded on the opening day but it's not like they were down to goalkeeping errors. Solid enough when called on and largely a quiet afternoon but for scooping the ball twice out of his net. Photo: Robbie Stephenson
2. Luke Ayling
5 - Far too high up the pitch for Cardiff's opener but offered plenty going forward. Photo: Robbie Stephenson
3. Liam Cooper
6 - Thundering, brave header from a corner to put his side back in it but the defence was all at sea for Cardiff's two goals although both stemmed from problems out wide. Stretchered off after injuring himself in scoring. Photo: Simon Hulme
4. Pascal Struijk
5 - Lucky to get away with an unfortunate slip in the first half on the edge of his area and also when Ugbo got in behind him after the break only to blaze over the bar. Photo: Robbie Stephenson
5. Leo Hjelde
4 - Still only 19 years old and a work in progress but Bowler got in behind him far too easily for the second goal. Subbed at the break for Byram who was undoubtedly an upgrade. Photo: Alex Caparros
6. Archie Gray
7 - Take a bow young man, what a debut, at 17 years of age. Far from perfect but looked immediately settled and also tried to cover at right back when Ayling bombed forward. Cool, calm, composed and also tried to get forward. A huge talent. Photo: Simon Hulme