The SD Worx team rider charged up the Via Santa Caterina climb in the final kilometre of the 136km race to gap Elisa Longo Borghini and secure victory in the opening UCI World Tour race for the 2021 season.
The result ended Annemiek van Vleuten’s recent dominance of the event with the Movistar rider missing out on a third consecutive title with her fourth-place finish.
With just over six kilometres to go, van den Broek-Blaak and her SD Worx teammates attacked leaving the peloton in their wake and only Longo Borghini in pursuit.
The Italian rider was no match for the 2017 World Champion who, with the support of her team, accelerated up the steep final climb to win ahead of Longo Borghini in second and fellow SD Worx rider Anna van der Breggen in third.
Van den Broek-Blaak praised the work of her team after the race and said without them she couldn’t have done it.
"This is unexpected. Wins like this one are the best ones in cycling," she said.
"The finale went very quick. I was in front in a small group with some other teammates. It was my job to attack.
"My team told me to sit back in Elisa's wheels. While Elisa was using up a lot of energy I managed to stay with her and eventually drop her on the last climb."
“This ranks as one of the biggest victories in my career."