Victory for the 28-year-old has seen Joshua retain his WBA and IBF titles while taking on Parker's WBO crown, potentially leaving the Brit with the opportunity to now take on the unbeaten Deontay Wilder for the final heavyweight belt in the division.
The win in Wales moves Joshua to 21 wins from 21 contests in a record that leaves the rising youngster with 20 knockouts and one win via unanimous decision. Parker is still to be knocked to the canvas, but has lost his unbeaten record which had previously stood at 24 fights.
Joshua started well and he set up an adroit defence of his titles by working cleverly off his jabbing left, leaving Parker frustrated on the outside as he struggled to find rhythm in the early rounds.
Britain's Joshua slowly edged ahead with more offensive work as he set about moving Parker around the ring, the New Zealander unable to find a route on the inside as Joshua's height and reach proved problematic.
There were few fireworks to speak of in Cardiff, but Parker grew comfortable during the middle rounds and finally found some speed to land a flurry of quick combinations, but once more Joshua's platform off the jab kept the 26-year-old at bay.
The evening's frustrating blemish came in the shape of referee Giuseppe Quartarone, who appeared far too keen to break up the fight whenever the two men sought to go toe-to-toe on the inside, which left Parker frustrated and at the mercy of a rein fight harnessed by Joshua.
Come the end of the 12th round, both fighters touched gloves in recognition of a night better remembered for some deft technical work from Joshua, as he proved that power is not the only weapon in his repertoire ahead of a potentially historic clash with Wilder later in the year.