After clearing that major hurdle, here is what lies ahead for the deal, the Prime Minister and Britain's exit from the EU.
Battle for parliamentary approval
Many thought it would be near-impossible for Mrs May to secure consensus among all of the EU's leaders back when Article 50 was triggered on March 29 2017. Furthermore, few predicted that one of the biggest threats to the deal would eventually come from Brexiteer MPs when, in the early stages of the negotiations, Remain campaigners took the Government to the highest court in the land in order to secure a meaningful vote for MPs. This Commons vote is the major hurdle Mrs May must now overcome if her hard-won deal is to be enshrined in UK law. The vote is expected to take place before MPs break for Christmas in December.
Led by figures including Boris Johnson and Jacob Rees-Mogg, a swathe of Brexiteer Tories have rejected Mrs May's deal and called for it to be renegotiated. This raises the prospect of some of Mrs May's own MPs voting against the agreement when it goes before the Commons. Appearing at the DUP conference on Saturday, Mr Johnson said the deal will leave the UK a "satellite state" of the EU. In the Sunday Express Mr Rees-Mogg said the deal "does not deliver" on Brexit and "instead of taking back control, in some areas it will leave the United Kingdom with even less control than it currently has: the vassal state".
The Eurosceptics' rejection of the plans stems in large part from the deal's backstop provision for the border between the Republic of Ireland and Northern Ireland. Hardline Brexiteers say it risks the UK being unable to ever fully leave the EU. The DUP say the backstop would see Northern Ireland adopt a different regulatory regime to Great Britain if a wider UK/EU trade deal fails to materialise. DUP leader Arlene Foster said the draft deal fails to protect the Union. With 10 MPs in the Commons, their support could be crucial for Mrs May's deal to pass.
Labour repeatedly warned that they would vote against any deal that does not pass six tests. Among the requirements are that it delivers the "exact same" benefits, fair management of migration and the protection of workers' rights and protections. On Wednesday Jeremy Corbyn branded the deal as "botched" and a "leap in the dark". "(It) breaches the Prime Minister's own red lines and does not meet our six tests", he said.
There is growing speculation that the deal will be voted down by MPs in its current form, although the PM is expected to have several weeks to build support. Aware of the widespread opposition among MPs, Mrs May is appealing directly to the public. On Saturday she issued a "letter to the nation" in which she urged Britons to get behind the deal. She has also sought the backing of business in an effort to encourage MPs to support the deal.
What happens if it is voted down?
MPs' rejection of Mrs May's plan would open up several possibilities - Britain crashing out of the EU with no deal on March 29, Mrs May having to return to the EU to ask for further talks or a so-called People's Vote that could see Brexit halted altogether. On Saturday Chancellor Philip Hammond warned that rejecting the deal would leave Britain in "uncharted territory", while he said a no-deal Brexit would unleash "economic chaos".
Could another deal be struck?
EU leaders have warned they will not return to the negotiating table, however a no-deal Brexit would have damaging consequences for both the UK and EU countries. If talks are re-opened it will likely mean extending the Article 50 period well beyond March 29. According to reports, officials in Westminster and Brussels are continuing to work on plans for alternative arrangements. The Sunday Telegraph reported that "several senior ministers" were working on plans for a Norway-style relationship with the EU.
Brexit: Part two
Negotiations up to this point have related to the arrangements for how Britain's divorce from the EU will take place. If Mrs May's divorce deal is passed by Parliament, next comes the long process of agreeing on how the UK will trade with the bloc in the future. Negotiators have until the end of the transition period, which could run until the end of 2022, to strike a deal. If they fail to do so that could mean the imposition of the backstop to ensure no disruption to the Irish border