A Tasmanian court has erupted in cheers after a jury found a 22-year-old man guilty of the stabbing murder of a rival inside central Hobart's Target department store.

Hobart man Jayden Montgomery plunged a stolen kitchen knife into Adrian Fitzpatrick's heart during a rolling fight through the city's shopping mall on September 29 last year, shocking a mid-week lunchtime crowd.

Montgomery had pleaded not guilty to murder, arguing he stole the knife from a Harris Scarfe store and acted in self-defence after seeing Mr Fitzpatrick, 24, in the mall and having taken a beating from him in a fight 10 days earlier.

The prosecution argued Montgomery acted out of pride and anger because he'd been humiliated in the earlier fight.

A Supreme Court jury found Montgomery guilty of murder on Friday after deliberating for 11 hours.

Mr Fitzpatrick's family and friends erupted with clapping and cheers when the verdict was delivered, prompting a warning from Chief Justice Ewan Crawford that he'd have them thrown out if the celebrations continued.

Montgomery is due to be sentenced next month.