After suffering several heavy defeats in the previous parliament, Johnson now enjoys a large majority and should face little opposition in passing the bill to implement Britain's biggest foreign and trade policy shift in more than 40 years.
More than three years since Britain voted to exit the European Union in a 2016 referendum, the deep uncertainty over Brexit has been replaced by the firm deadline of Jan. 31.
"Today we will deliver on the promise we made to the people and get the Brexit vote wrapped up for Christmas," Johnson said before the vote, expected to take place at around 1430 GMT.
"Then, at the beginning of the new decade, at the beginning of a new dawn for our country, our parliamentarians will return to Westminster to immediately finish the job, take us out of the EU on the 31st January and move this country forward."
The final stages of ratification will take place after Christmas, but Johnson wants to hold a vote before then as a sign of his intent.
After leaving, Britain will need to secure new trading arrangements with the EU. The so-called withdrawal agreement bill seeks to make sure that there can be no legal chance of extending those talks beyond the end of next year.
Just a week after he won the largest Conservative majority since Margaret Thatcher in 1987, Johnson has set out an ambitious government program with securing Brexit at the top of his agenda to repay the trust of voters.
Hoping to satisfy the demands of voters in northern and central England who broke their tradition of backing the opposition Labour Party to support him, he has also pledged more funding to the state health service, education and policing.
"After years of delay and rancor in parliament, we will deliver certainty, and hard-working businesses and people across this country will have a firm foundation on which to plan for the future," he said."Next year will be a great year for our country."