Eric Mendelsohn and Serge Chermayeff's 1930s masterpiece was originally scheduled to reopen last month, following an 18-month refurbishment masterminded by John McAslan + Partners.
Thanks to the £8 million renovation programme, the Grade I-listed Modernist favourite now boasts a new studio space, galleries, a shop and terraces, as well as a fully restored 1,000-seat auditorium.
Funded by the Arts Council, English Heritage and a number of charities, the project has transformed the pavilion into one of the largest contemporary art galleries in south-east England.
During the opening weekend, visitors will be able to take a first look at a range of new exhibitions and the event will be marked by a specially commissioned choral piece called Sea Tongue.
The day will be topped off with a massive firework display.