The mild weather meant it was one of the largest crowds ever to attend the event.
Olympic silver-medal winning rowers Gary and Paul O'Donovan had the honour of leading the countdown and turning on the lights with the Lord Mayor of Cork Cllr Des Cahill.
Students from The Academy of Popular Music provided musical entertainment on the stage set up outside Easons from 6.30pm.
By the time the lights were switched on at 7.15pm the crowds stretched the full length of Patrick's Street to reach Waterstones bookstore.
Extra screens were installed at the junction of Academy Street to allow the thousands of visitors to watch the proceedings on stage.
A major traffic management operations as put in place for yesterday's event with a number of streets closed and traffic diversions in place.
The large crowds meant traffic delays occurred after the event with An Garda Siochána reporting delays on South Mall, Parnell Place, Merchants Quay, Grand Parade and Washington St. There were also lengthy delays for cars exiting the Paul Street multi-storey car park.
The switching on of the lights marked the beginning of the Christmas season in Cork and a big promotional drive by Cork City Council and the Cork Business Association to encourage people to come into the city centre to shop in the lead up to Christmas.
Cork will be transformed into a festive wonderland with the opening of GLOW, A Cork Christmas on the Grand Parade on November 25, which will run for four weekends in the build up to Christmas.
Once again Bishop Lucey Park will be transformed inot a Christmas wonderland with street and food stalls located on Grand Parade.
The Dates for GLOW this year are Friday, November 25 to Sunday 27; Friday, December 2 to Sunday 4; Friday, December 9 to Sunday 11; Friday, December 16 to Sunday 18.