The Briton's controlled aggression saw him inflict the first inside-the-distance defeat of Wallin's career, with the Swede's corner pulling him out of action after the end of the fifth round of a one-sided contest.
Victory gave Joshua his third win from as many bouts in 2023 after he beat Jermaine Franklin Jr. by unanimous decision in April before a seventh-round stoppage success against Robert Helenius in August.
It also took Joshua's professional record to 27 wins and three defeats.
Joshua dominated right from the opening bell, with Wallin's nose bloodied in the first round by the two-time former world heavyweight champion.
Parker overpowers Wilder
Earlier on the same bill, Joseph Parker (31) - once beaten in a title fight by Joshua - defeated former WBC heavyweight champion Deontay Wilder (38) with a unanimous points decision win.
Parker, who held the World Boxing Organisation title, was too strong and too skilled as he comprehensively defeated Wilder in what was the former World Boxing Council champion's first bout in over two years.
Renowned as a powerful puncher, Wilder was involved in a trio of dramatic bouts with current WBC champion Tyson Fury, drawing the first before losing the next two.
Wilder's long period of inactivity appeared to count against him, with Parker landing the cleaner punches as well as producing several thumping roundhouse rights.
The American briefly rallied in the eighth round but did well to make it to the bell as Parker hit back with several telling blows in a comprehensive victory.
