Thousands of people are estimated to have visited the event, which took place on the boardwalk.
Saturday’s free event aimed to give visitors of all ages an insight into the emergency services, and featured a line-up of vehicles from a variety of emergency services.
Port Solent welcomed a range of vintage police cars and fire engines on display for visitors to explore and enjoy, as well as working vehicles.
Visitors had the chance to see inside the vehicles and meet those who work for Hampshire Fire and Rescue, Raynet (Emergency Communications Service), Hampshire Police, the RNLI, South Coast Ambulance Service, and Hampshire and Isle of Wight Air Ambulance.
Families stood in long queues to see inside ambulances and police cars, with one mum saying she had been waiting upwards of 20 minutes.
She believes that the big turnout is due to a lack of events happening due to the pandemic, and said: 'It's because there hasn't been anything like this going on for a while.'
The event was organised by Port Solent, along with people who take part in the Port Solent car meets.
Lisa Fowler, Port Solent's events, marketing and centre administrator, said: ‘It’s been brilliant, really good - we were running out of parking.
‘It’s lovely, so nice to see so many people enjoying themselves doing something normal.’
Port Solent has hosted a 999 Day a couple of times before, but the pandemic meant that the event was not held in 2020.
Youngsters enjoyed face painting, and had their picture taken with fire investigation dogs.
They could also investigate inside an old police car and USA cop patrol vehicles.
There were also a number of stalls from organisations and charities, including Solent Rescue Independent Lifeboat and the RNLI.
Margaret Fleming, of Portsmouth, has volunteered with the RNLI for 31 years, and hosted a stall selling items to raise funds for the charity’s work.
She said: ‘We’ve been very busy, mostly selling toys for the kiddies, as well as cards and calendars.’
Port Solent’s 999 Day will make a return next year.