Konta threatened to take the match to a decider in the second set after battling back from 4-0 down – losing eight games in a row – to force a tie-break at the Pat Rafter Arena.
The British number one came from a set behind to defeat Tomljanovic at the same stage in Brisbane last year but there was to be no repeat in 2019 as the Croatian-born Australian prevailed in one hour and 21 minutes.
Kvitova beats Britain's Konta, Barty to face Azarenka
Konta, ranked nine places higher at 37 in the world, was comprehensively outplayed in the first set and in the eighth game she conceded two set points on her own serve.
The 27-year-old, who won only 50 per cent of first service points, was broken for the second time to slip a set behind when hitting a simple forehand wide.
A lengthy rally early in the second set ended when Konta’s accuracy deserted her and having been tied at 2-2 in the first set, the Sydney-born Briton had failed to win a single game since as she fell 2-0 behind in the second.
It was not until the 13th game that Konta secured her first break point of the match and finally she broke her opponent’s grip to offer hope of a comeback.
She also won the next game and 4-0 had become 4-3, prompting Tomljanovic to consult her coach, but that failed to immediately pay off as the score was levelled.
Three unstoppable first serves helped propel Tomljanovic back into the lead, however, before the tie-break was registered with every point now being fiercely contested.
The authority that had deserted the home favourite was now restored as Tomljanovic clinched her place in the quarter-finals with an ace.
Osaka extends win streak in first match since Australian Open
WTA Adelaide International
Konta knocked out of Adelaide International in last-16