Cardiff Council approved the clubs application on Wednesday to increase capacity of Cardiff City Stadium to 33,000.
The extra 5150 seats will be added when a new tier is built on the Ninian Stand.
Work is likely to start soon as the club want to have the stadium upgrade complete before the stadium hosts the European Super Cup next August. That features the winners of the Champions League and the winners of the Europa Cup facing each other. In 2013 the match was Bayern Munich v Chelsea.
Throughout the season the roof will be removed and then the new level added which will include the extra seats and also a new hospitality area.