Buckland was born in Llanelli in 1968, and was educated at Old Road County Primary School and St Michael's School in the town and at Hatfield College, Durham, where he became Secretary of the Junior Common Room and President of the Durham Union Society. He graduated in Law in 1990 and was called to the Bar at Inner Temple in 1991.
Buckland practised as a barrister from 1992 to 2010, specialising in criminal law. In 2009, he was appointed as a Recorder, sitting a part-time Judge in the Crown Court. He became a Queen's Counsel in 2014 and a Master of the Bench at Inner Temple.
He was a member of Dyfed County Council from 1993 to 1996, having won his Elli Ward seat from Labour with a majority of just 3 votes. It was reported that he was the first Conservative "in living memory" to have been elected in the Llanelli area. In 1994, Buckland stood for the safe Labour European Parliament seat of South Wales West. Buckland stood for the Conservatives in the by-election for the Welsh constituency of Islwyn caused by the appointment of Neil Kinnock as European Commissioner. The by-election was held at a time of unpopularity for the Major government, and was won by the Labour candidate, Don Touhig. Buckland polled only 3.9%. He also stood for Preseli Pembrokeshire at the 1997 general election and was on the Conservative list of candidates for Wales at the 1999 European elections.
In 2005, Buckland was selected as the Conservative Party's prospective Parliamentary Candidate for Swindon South, replacing former MP Simon Coombs who had represented Swindon between 1983 and 1997, and had unsuccessfully contested the seat in 2001. At the 2005 general election, Buckland lost to Labour candidate Anne Snelgrove, who polled 17,534 votes to his 16,181, a narrow majority of 1,353 votes.
In the 2010 general election, Buckland won the South Swindon seat with a majority of 3,544 votes, a swing of 5.51% to the Conservatives, defeating the incumbent MP Anne Snelgrove. He obtained 19,687 votes, (41.8% of the total) compared to 16,143 votes for Snelgrove.
In the 2015 general election, Buckland held the South Swindon seat with an increased majority of 5,785 votes, a swing of 2.2% to the Conservatives and an increase of 4.5% in the Conservative vote. He obtained 22,777 votes (46.2% of the total) compared to 16,992 for Labour.
In the 2017 general election, Buckland held the South Swindon seat with an decreased majority of 2,484 votes, a swing of 3.5% to the Labour but with an increase of 8.9% in the Conservative vote. He obtained 24,809 votes (48.4% of the total) compared to 22,347 for Labour.
In 2010, Buckland was elected to the Justice Select Committee. In 2012, Buckland along with fellow Tory MP Stuart Andrew, called for prisoners' mobile phones to be destroyed or sold to raise money for victims' charities, saying that mobiles in prison were a "menace" and that selling them would provide a service to the country, as it costs £20,000 a year to store criminals' phones. They were both supported by Parliamentary Under-Secretary of State for Legal Aid and Legal Services Jeremy Wright and Shadow Secretary of State for Justice Sadiq Khan. He Chaired the All Party Group on Autism from 2011 to 2014 and was an officer of the All Party Group on Speech, Language and Communication.
On 4 December 2012 Buckland was elected Joint Secretary of the influential 1922 Backbench Committee. He was also Chair of the Conservative Human Rights Commission from 2011 to 2014. He also sat on the Standards Committee and the Privileges Committee from 2012 to 2014. He also served on the Joint Committee on Human Rights from 2013 to 2014 and the Joint Committee on Privacy and Superinjunctions which was convened from 2011 to 2012.
On 15 July 2014, Buckland was appointed Solicitor General for England and Wales, replacing Oliver Heald as part of a wide-ranging government reshuffle. Shortly after the reshuffle, his appointment attracted some criticism over a disciplinary finding he had once received from the Bar of England and Wales that related to voluntary work as a school governor prior to his election as an MP. In response, the Attorney General's office stated that Buckland's breach had been "minor" and that the finding "was removed from the Bar records after two years and therefore Mr Buckland was not required to declare it upon appointment as Solicitor General."
As Solicitor General, Buckland took the Serious Crime Bill 2014 (now the Serious Crime Act 2015) through its Commons stages in Bill Committee. The Bill contained provisions that, amongst other things, updated the criminal law of child neglect and introduced a criminal offence of coercive control of people within close relationships in a domestic context. As a backbencher, he had campaigned on these issues. In 2015, he worked with Home Office Minister James Brokenshire to take the Immigration Bill through its Commons stages. In 2016, he successfully helped to take the Investigatory Powers Bill through its Commons stages.
In 2011, Buckland was awarded the Politician of the Year Award by the Royal College of Speech and Language Therapists for his campaigning work on speech, language and communication issues. In January 2013, Buckland was awarded the Grassroot Diplomat Initiative Award under the Social Driver category for his extensive work on advocating awareness at parliament for children with special educational needs, including those with autism both locally and nationally.