Ms Brabin got more votes than Bradford council leader Susan Hinchcliffe and lawyer Hugh Goulbourne. Party members from across the county were balloted as part of the selection process.
She will likely be the favourite to win the mayoral election next May, despite the Conservatives' success in West Yorkshire in December's General Election. The Tories have yet to choose their candidate and no possible contenders have declared themselves publicly.
She said: "I’m Yorkshire through and through, so this is a huge honour. I’m incredibly proud to be Labour’s mayoral candidate because it means representing the people I grew up with and the communities I grew up in to try and make a real and practical difference to their day to day lives.
“We’ve seen this year, more than any other, how much it matters who we elect. We need a mayor who is going to get West Yorkshire our fair share when it comes to funding, jobs, transport and a recovery from the pandemic. There’s a big north/south divide in this country and we deserve better that to be treated as second class citizens.
“There’s a big job to do in rebuilding our economy in a post-Covid19 world, my job will be to make sure that what comes next is fair and delivers the jobs, skills and opportunities people in our cities, towns, villages and former mining communities deserve.”
Labour's shortlisted candidates were agreed earlier this year by a joint selection panel made up of the party's ruling National Executive Committee and regional officials following interviews.
There followed a campaign and hustings period, with the ballot opening on November 23.
Ms Brabin, a former Coronation Street actor who served in Jeremy Corbyn's Shadow Cabinet, says her “immediate priority will be to build on work underway already to establish a Job Creation Taskforce to create good, unionised jobs and retraining opportunities”.
She has been endorsed by Doctor Who star Jodie Whittaker, who described her as "a beacon of real and exciting change".
Coun Hinchcliffe, who was born and bred in Bradford, also chairs the West Yorkshire Combined Authority and was heavily involved in the devolution talks which led to the creation of the mayoral role.
Her key pledges to win the support of Labour members for the party’s candidacy are focused on equality, prosperity for all communities, a cleaner, greener economy, 21st century transport and housing.
Mr Goulbourne writes on his website that he was shaped by his background growing up as a "mixed-race kid" in Coventry in the 1980s "amid neglected, divided communities, and surrounded by factory closures, crumbling schools and hospital waiting lists".
The father-of-two advised the last Labour government on fuel poverty and environmental issues and says that as a lawyer he is "used to working with business leaders locally and internationally in a wide variety of sectors".
The mayoral election will take place on May 6 next year and whoever is elected will gain control over a host of budgets and powers previously held by central government.
The elected mayor for West Yorkshire - which takes in Leeds, Bradford, Wakefield, Calderdale and Kirklees - is also expected to take on the powers currently held by the police and crime commissioner.