Taking to the stage amid heckling from defeated right-wing opponents, Mrs Brabin restated her commitment to pursuing a politics of "unity and hope" in the wake of Jo Cox's death.
She also pledged to be a "strong Yorkshire voice" for every single one of her constituents, and to work tirelessly to protect local services "from Tory cuts".
The speech marked the end of an intense and emotional election campaign, which was triggered by the tragic death of Mrs Cox in June.
Turnout for the ballot was just 25.78%, with Mrs Brabin securing 17,506 (85%) of the total 20,300 votes cast.
As she took to the stage, the former Emmerdale actress was heckled by defeated right-wing candidates, some of whom could be heard shouting "racist" and "fascist".
This did not stop her celebrating her victory, as she paid tribute to Mrs Cox and her family, and thanked voters for their support.
"This will be a particularly difficult day for Jo’s family and friends, and I want to pay tribute to them – we are all thinking of you and will always stand side by side with you," she said.
"I want to pay tribute to the other mainstream parties for recognising the deeply sad nature of this by-election and deciding not to stand.
"I have met so many people over the last few weeks who have told me they didn’t usually vote Labour but were lending me their support this time.
"Some because of what Jo meant to them. Some because they wanted to send a message that our community stand united. Some as a reaction to some of the fringe parties who chose to try and use this tragic by-election as an opportunity to sow division.
"Whether you voted for me, voted for other candidates or didn’t vote at all – I give you my word I will be an equally strong voice for each and every one of you."