The 144-year-old structure was almost destroyed in 2010 but the attraction reopened to visitors in April.
An official opening on Saturday included speeches from funders and politicians before celebrations started on the Sussex town's pier.
The gala day was finishing with a concert headlined by Madness.
Simon Opie, chief executive of Hastings Pier Charity, said it was a "tremendous" moment.
He said: "It's a great relief in many ways to reach this stage, but also tremendous to be able to celebrate what has been achieved and to have so many of our shareholders and supporters here on the pier enjoying what has been created."
The £14.2m redevelopment took more than two years and saw the pier's former pavilion turned into a restaurant and bar.
The council has said it is hoped the restored pier will re-energise the town, not just as a tourist destination but as a local facility and generate more than £1m a year for the local economy.
The pier, built in 1872, was prosperous during the mid-20th Century, but it saw a decline as holidaymakers travelled further afield.
It was closed for safety reasons in 2006 because it had fallen into disrepair and then fire tore through the structure in 2010.
Work to redevelop the pier began after the council compulsorily purchased it from its owners in 2012.
The structure is now owned by the Hastings Pier Charity and 3,000 shareholders who bought into the project at £100 a share.
Hastings Pier has been officially opened after a multimillion-pound redevelopment that followed a devastating fire.