Dunedin’s Harris (23) led home the New Zealand riders in the 158km road race from Antwerp with circuits around Flanders before the finishing loop in Leuven.
Team-mates Michaela Drummond and Henrietta Christie were in the front group over the early stages looking for opportunities to get into a break but the high pace negated any attacks.
That left the World Tour pair of Harris and Niamh Fisher-Black to position themselves at the pointy end of the peloton over the final two and a-half laps of a testing circuit in Leuven.
Harris was able to maintain position in the front group as attack after attack launched over the final laps. She was caught on the wrong side of a split in the lead group on the penultimate climb, the Kiwi coming home in the second pack, 49sec behind the winner.
Young Italian rider Elisa Balsamo, a former junior world champion on the track and road, upset Dutch star Marianne Vos for the honours.
Drummond, in her first elite road world championships, came home in the third chase group 9min 13sec down on the winner in 64th place with Fisher-Black a further 20sec back in 91st place.
“I am really happy with my ride,” Harris said.
“I knew if I got my position right then I could have a good race as long as I did not have any bad luck getting caught in crashes. I am really happy with a top-30 place.’’
On Saturday, Southland Olympian Corbin Strong battled through a brutal and crash-ridden 161km race to claim a top-20 finish in the peloton of the men’s under-23 road race.
Italian Filippo Baroncini edged off the front as the peloton, including Strong, mopped up the break on the final climb, but not before both New Zealand riders Logan Currie and Finn Fisher-Black made bold moves at the front of the race.
Canterbury rider Currie took his chances to get into an early break, avoiding the swag of crashes that produced mayhem behind, and accounted for under-23 national champion Jack Drage, who broke his bike frame in a crash to bring an early finish to his race.
Currie pushed to the lead with a select group, opening a 4min lead in the loops around the Flanders circuit, until a puncture — and being sent the wrong way by officials — dropped him back in the pack with 60km remaining.
National under-23 time trial champion Fisher-Black took up the challenge as the race moved back to the circuit around Leuven, pushing into an eight-strong break that opened a 1min advantage.
However, he could not go with the final acceleration on the toughest climb with just over a lap remaining, leaving Strong to hold on to the bunch which reeled in the leaders with the finish in sight.
Baroncini made the attack and held on to win with Strong in the 32-rider peloton that finished just 2sec back.
Queenstown cyclist Reuben Thompson, who moves to the World Tour with his Groupama-FDJ team, was 2min 28sec back in 54th.
Fisher-Black, already with UAE Team Emirates, rolled home 7min 28sec back in 85th with the courageous Currie a further 2min behind.
