James White, from Southampton, was said to be in "good spirits" following the ordeal.
Astley himself has described the event as "the definition of crazy".
Originally James' brother Jack had started the challenge but had to stop due to internet trolls hacking his live stream on YouTube.
The singer, who had a string of hits in the 1980s, had himself even lent his support by posting on Facebook.
The challenge finished at 15:00 BST on Monday, by which time the song is thought to have been played at least 2,500 times.
More than Â£6,000 has so far been raised for research into diabetes.
The Juvenile Diabetes Research Foundation (JDRF) South charity posted on Facebook: "Hats off - it's been a fundraising event of epic proportions and we thank you from the bottoms of our hearts!"
Jack White, 23, a choir-master from Southampton, began the 75-hour lock-in with the 1987 hit Never Gonna Give You Up set to repeat, on Friday at noon.
However in a Facebook video message around eight hours into his charity bid, he said he had been inundated with abuse on his live YouTube page.
The trolls also attacked his seven-year-old nephew who has Type 1 diabetes and for whom Mr White was fundraising.
His brother James took over the challenge instead, which also included not washing, not browsing the internet and living on a diet of porridge, rice and water.
Astley's 1987 opus was part of the "Rickrolling" phenomenon, where millions of people were duped into clicking on a web link directing them to a video of the song.
A man has emerged from a charity lock-in where he has spent the weekend listening to 1980s Rick Astley hit Never Gonna Give You Up on repeat.