Campbell Mickel, 51, got the rare fish after buying it from traders in Barcelona - and said he was so excited he couldn't sleep.
It arrived in the UK on Monday and was transported to Eddie's Seafood Market, Edinburgh, overnight.
It took four guys to haul the huge tuna onto the window display at the famous fish market - and Campbell said he will have to fillet it in on the floor as it doesn't fit on the counter.
Campbell said he would not normally advocate eating bluefin tuna but said the 7ft fish was farmed rather than caught in the wild.
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It was captured at a young age and farmed in a pen in the Mediterranean until it matured before being sold.
Campbell was asked by a customer who owns a sushi restaurant to source the bluefin.
He spent nearly three months trying to find the fish, which he said it worth thousands.
Campbell will now spend around two hours cutting it up into four fillets before handing it over to the owners of sushi restaurants Bentoya and Kenji in Edinburgh.
The fish will be super frozen at minus 60 degrees to protect the quality of it.
Campbell, whose famous shop is based in Roseneath Street, Marchmont, said: "I bought it from Barcelona on Friday and it arrived in the UK yesterday after being transported overnight - I didn't sleep at all last night I was so excited.
"It weighs 150kg and is about 7ft long.
"Bluefin tuna are highly endangered so we wouldn't normally advocate eating it.
"But this one was caught when it was young and farmed until it was mature in a pen - so it's classed as farmed as opposed to wild.
"It was farmed in the Mediterranean off the east coast of Spain.
"I bought it through traders in Barcelona and they handle everything needed to get it to the UK.
"It cost me a thousands.
"It took four of us to try and get it on display but we had to really wrestle with it, you can't get your arms around it at all and it's so slippery.
"You can't comprehend the size of this fish until you see it in real life.
"It has been sold to one customer, a sushi restaurant, who will super freeze it to minus 60 degrees to protect the quality of it.
"The customer asked me to located the fish for him and I have been working on it for two or three months.
"We supply sushi restaurants in Edinburgh, Glasgow and Dundee but we don't normally deal with bluefin tuna.
"But because this was a farmed product I wanted to try it.
"For a sushi restaurant this fish is as good as it gets, it's the creme de la creme - it's their lobster, caviar and champagne all in one meal."