As thousands lined the foreshore of Sydney Opera House, others were partying on waterfront balconies and yachts to mark the historic occasion.
Many are waving pink banners, with one reading: "Welcome Home Jess" and another "Jessica, Sydney salutes you".
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The 16-year-old Queenslander, who hoped to go down in history as the youngest person to circumnavigate the globe solo and unassisted, crossed the Sydney Heads finish line Saturday afternoon.
Spectators began arriving hours early to get the best spots including fellow Queenslanders Judy and John Matthew who came to salute the "brave young girl".
The couple admitted to being sceptics early in Jessica's voyage but changed camp when the teenager sailed around South America's Cape Horn.
"We have been following her every day since she started," Ms Matthew said.
Her husband said the teenager had proved them wrong through her determination and stamina.
"I wouldn't want to do it - no hot shower for seven months," Mr Matthew said.
Sydney teenager Alana MacIntyre, who came with her mum Sylvana and grandmother Edna, says she has been inspired by Jessica's efforts.
"She has got loads of courage to go and do it because you don't know what's out on the ocean," she said.
"Jess is a big inspiration. When I think of her it encourages me to do smaller things. Just to believe in yourself and not give up."
The congratulations were literally sky high with an aeroplane flying over the Harbour writing "Jessica" in the blue heavens.
But the excitement appeared to be too much for one elderly woman who collapsed and was carried away on a stretcher by paramedics.
