1st term as MP (2010-2015)

At the 2010 general election, Garnier was elected to Parliament as MP for Wyre Forest with 36.9% of the vote and a majority of 2,643.^[13][14][15]

Garnier made his maiden speech on 7 June 2010, where he set out his scepticism about further integration in the European Union, and focused on the economic and trading gains to be had from trading relationships.^[16]

Garnier previously served on the Treasury Select Committee and raised a debate in the House on Commons on 29 November 2010 (with several other Conservative MPs) on the regulation of independent financial advisers.^[17] Garnier also serves on several All-Party Parliamentary Groups and was previously Deputy Chairman of the APPG concerning Space.^[18]

Throughout his time in Parliament, Garnier, himself a smoker, has campaigned strongly to end tobacco smuggling. In 2012 it was reported he had accepted tickets for the Chelsea Flower Show from Japan Tobacco International (JTI), costing £1,100. Commenting on this he said: "All of us who are MPs in Worcestershire have taken pay cuts of some form or other from coming out of the private sector... If we wanted to have our nose in the trough I could go back to being an investment banker. The reason I'm an MP is the complete opposite to having my nose in the trough. Two years of hundred-hour weeks. To pick on this one thing is really irritating".^[19]

In a speech on 19 January 2012, Garnier criticised a Labour proposal to set a minimum age for owning a shotgun certificate, arguing that shooting was a major competitive sport and that based on Countryside Alliance statistics there was "no reason" to feel uncomfortable with under-10s having licensed access to shotguns.^[20]

Also in January 2012, Garnier, along with fellow Conservative MP Richard Harrington, spoke about the right environment for business to be essential. He thinks can be achieved for young people through vocational courses in higher education that offer practical skills to become entrepreneurial.^[21]

Garnier was named by the ConservativeHome website as one of a minority of loyal Conservative backbench MPs not to have voted against the government in any significant rebellions in September 2012.^[22] Garner was subsequently one of 80 Conservative MPs to oppose the Coalition's Marriage (Same Sex Couples) Act 2013.

In November 2014, Garnier voiced his support for HS2, believing that Birmingham Airport will be an increasingly significant hub for the region that will help to ease pressure on Heathrow.^[23]

In December 2014, Garnier was criticised by Labour's Jonathan Ashworth for comments he made during a speech at the Institute of Economic Affairs. Garnier said of the need for a stronger message to Conservative supporters: "We need to be giving a much clearer message to them that they don't have to worry about politicians mucking around with tax rates in order to try and attract a few dog-end voters in the outlying regions of the country." Garnier later said: "If I used slack language in order to make a point, I am sorry if I caused any offence to anybody. I believe every voter is important everywhere".^[24]

2nd term as MP (2015-2017)

At the 2015 general election, Garnier was re-elected as MP for Wyre Forest with an increased vote share of 45.3% and an increased majority of 12,871.^[25]

Since July 2015, Garnier has been the vice-chair of the All Party Parliamentary Group for Space.^[26]

In December 2015, Garnier expressed disappointment at the decision of the regulator not to investigate the incentives, pay and culture of banks and their potential association with misconduct including the Libor scandal.^[27]

Garnier was the local MP of Natalie Connolly, a woman killed in 2016. Garnier, alongside MP Harriet Harman have since taken action to resolve the issues of the "rough sex" defence by advocating amendments to the Domestic Abuse Bill in England and Wales.^[28]

In the lead-up to the 2016 EU membership referendum Garnier supported Remain.^[29] In October 2017, he said that 'doom-mongers like himself' had been proved wrong since the Brexit vote.^[30]

On 17 July 2016, he was appointed to the newly created position of Parliamentary Under-Secretary of State for International Trade but was dismissed on 9 January 2018 after the cabinet reshuffle.^[31]

3rd term as MP (2017-2019)

Garnier was again re-elected at the snap 2017 general election with an increased vote share of 58.4% and an increased majority of 13,334.^[32]

In October 2017, the Cabinet Office began an investigation into a potential breach of the ministerial code after The Mail on Sunday revealed he had sent an aide, whom he called "sugar tits", to buy two vibrators from a sex shop while he waited outside, allegedly one for his wife and one for a colleague who worked at his constituency office.^[33][34] The investigation, which reported on 21 December 2017, concluded that Garnier did not break the ministerial code (the incidents having occurred before he was appointed) and had not acted inappropriately since becoming a minister.^[35]

4th term as MP (2019-)

At the 2019 general election, Garnier was again re-elected with an increased vote share of 65.2% and an increased majority of 21,413.^[36]

In July 2020, Garnier was selected as chair of the Committees on Arms Export Controls.^[37] The committee examines export licensing decisions, such as the decision to resume exports to Saudi Arabia. Private Eye reported that, in 2018, Garnier had taken a 5-day trip to the kingdom, with Saudi Arabia paying the £7,000 cost.^[38]

In August 2021, former Carshalton and Wallington Liberal Democrat MP Tom Brake, now Director of Unlock Democracy,^[39] wrote to Chris Bryant MP, the Chair of the Commons Select Committee on Standards, to examine the dual roles of those MPs who sit on APPGs while also having paid appointments in the sectors of interest of the APPG.^[40] In October 2021, Bryant announced a new "wide-ranging" inquiry into APPGs and into the rules regulations governing these unofficial parliamentary groups.^[41]

In November 2021, Sky News political reporter Sophie Morris reported how Garnier had spoken in the Commons on 22 separate occasions since November 2019, and in three of those appearances had urged fellow MPs to give more support to the space sector.^[42] Garnier has urged the adoption of a "three-point strategy" that would enable the UK to have a "cohesive and coherent space policy."^[42]

Garnier was appointed Officer of the Order of the British Empire (OBE) in the 2024 New Year Honours for political and public service.^[43]