Mitchell was born Gareth James Mitchell^[3] in Eastleigh, England to a Welsh father,^[4] Colin Mitchell.^[5] He spent his childhood in Montgomeryshire,^[6] Powys, Wales.^[7] When Gareth was seven, his father lit up a bulb with a closed circuit, and that sparked his interest in science.^[8]

He was a member of the computer society at school (Welshpool High School) and participated in bellringing^[9] and organ playing^[10] at his local church. As an undergraduate studying Electrical and Electronic Engineering at Imperial College London, Mitchell joined campus radio working behind the scenes, but saw that "[t]he people who seemed to be having all the good fun were the creative types in the studios."^[11] Because of that, after getting his engineering degree and relevant work, he took up an MSc in Science Communication, also at Imperial.^[12]

Mitchell joined the BBC during the mid-1990s, starting his career as a broadcast engineer. His initial dream was to be part of Tomorrow's World,^[13] BBC's flagship technology TV programme, but a visit to a radio studio at Bush House got him obsessed about radio journalism.^{[14][failed verification]} Mitchell eventually decided to trade climbing TV and radio transmitter towers for science and technology journalism. He had worked for Radio Netherlands on science programmes.^{[citation needed]}

His first hosting role on the BBC was for the youth science program, The Lab.^{[15][failed verification][16]} Occasionally, he had also presented Science in Action and The Science Hour on the BBC World Service, and reported on the television programme Click.^[17]

He presented on the BBC most notably as the host of Digital Planet (previously known as Click^[18] and Go Digital^[19][20][21]) a BBC radio programme broadcast worldwide on the BBC World Service with Bill Thompson until its end in March 2023.^[2] During his time on the show he interviewed people such as Jimmy Wales,^[22] Stephen Fry,^[23] Professor Dame Wendy Hall,^[24] Martyn Ware,^[25] Feargal Sharkey,^[26] Jean Michel Jarre^[27] and Vint Cerf.^[28] From time to time, he is a stand-in presenter for BBC Inside Science on BBC Radio 4. Additionally, Mitchell wrote for the Q&A section of BBC (Science) Focus Magazine and hosted the Q&A podcast^[29] from 2008 to 2017.

After the end of Digital Planet, in April 2023, Mitchell and Thompson returned with a new technology podcast, The Gareth and BillCast^[30] as well as Mitchell presenting ""Somewhere on Earth: The Global Tech Podcast"^[31]

Mitchell has lectured at Imperial College London since 1998 in broadcast and written journalism on the Science Communication and Science Media Production MSc programmes ^[32][33] since 2000^[34] and 2002 respectively.^[35] He also presents the Imperial College Podcast. The key event leading to his appointment as a radio tutor was a bet in a pub over a Guardian job advertisement for that role.^[36][37]

He emceed TEDx Imperial.^[38] He has attended the World Economic Forum^[39] and has hosted workshops, discussion panels and conferences on science and technology.^[40][41][42]

At Imperial he has cofounded, and now runs, the "Science Media Diversity Scholarship".^[43] The award covers tuition fees and London living costs for a year, for a student from a minority ethnic group. The Science Media Diversity Scholar also completes an internship at one of the sponsoring television production companies.^{[citation needed]}

As well as broadcasting and lecturing Mitchell is an host and facilitator at big events with clients such as the European Commission, OECD,^[44][45] World Economic Forum,^[46] Wellcome Trust, and Nesta.^{[citation needed]}

Apart from the bells and the organ, other instruments Mitchell can play are the piano and keyboard.^{[citation needed][47]} He rides motorcycles, has taken flying lessons, and has been a licensed amateur radio operator since August 2019.^[48][3] with his call sign M7GJM. He continues to use his engineering skills by for example has developing a way to provide the required signal needed for the studio clocks^[37][49] he'd bought at an auction for items from Bush House, the BBC World Service's former headquarters, he did this by making a Master clock from a microcontroller called an Arduino.

• Gareth Mitchell's YouTube videos
• Gareth's OpenLearn articles Archived 7 October 2013 at the Wayback Machine for the Open University
• Gareth Mitchell's articles for BBC Science Focus Magazine
• Gareth Mitchell on Twitter