Guangzhou held the upper hand after earning a 2-2 draw from the first meeting in South Korea last month and they further strengthened their grip on the final when Elkeson deservedly put them ahead in the 58th minute.
Seoul quickly responded with an equaliser from Dejan Damjanovic but they could not find a winning goal in the last 28 minutes which would have seen them clinch the title as the tie finished 3-3.
The success was no more than Marcello Lippi's side deserved after bossing the clash in front of more than 42,000 fans at their Tianhe Stadium.
The Chinese Super League champions created virtually all of the chances in the first half but Elkesen could not take advantage of several openings while Zhao Xuri headed over and Dario Conca struck the woodwork.
Luiz Muriqui was then denied by visiting keeper Kim Yong-dae after going clean through at the start of the second half, while China international Huang Bowen also saw his shot saved soon after.
Guangzhou finally got the breakthrough in the 58th minute when Elkeson scored his sixth goal in six Champions League games after picking up a pass from fellow Brazilian Muriqui.
That seemed to spark Seoul into action and four minutes later they drew level through Damjanovic, who followed up his late equaliser in the first game with another goal after being set up by Sergio Escudero.
The two teams went in search of a winner after that but were unable to produce anything to seriously trouble the respective goalkeepers as Guangzhou held on for the title.