Bhagat Singh Koshyari was born on 17 June 1942 to Gopal Singh Koshyari and Motima Devi at Palanadhura Chetabgarh, Bageshwar District, Uttarakhand.
Koshyari holds a master's degree in English and studied at Almora College, Almora of Agra University, now S.S.J. Campus Almora of Kumaon University. During this period, Koshyari was also a general secretary of the students' union of Almora College, Almora, between 1961-62. He has also represented the Executive Council of Kumaon University, during 1979-82, 1982–85 and 1988-91.
He has had a successful career as a teacher and journalist. He had worked as a lecturer at Raja Inter College, Raja Ka Rampur, Etah district, Uttar Pradesh for few years. Koshyari is a founder and managing editor of Parvat Piyush, a weekly published from Pithoragarh, Uttarakhand since 1975. He has also published two books, Uttaranchal Pradesh Kyun? and Uttaranchal Sangharsh Evam Samadhan.
He joined the Rashtriya Swayamsevak Sangh (RSS). He took part in the struggle against the Emergency and was imprisoned he was detained in Almora and Fatehgarh Central Jail under the Maintenance of Internal Security Act (MISA), from 3 July 1975 to 23 March 1977.
In May 1997 he became a member of Uttar Pradesh Legislative Council, the upper house of legislature of Uttar Pradesh. In 2000, he was appointed minister of Energy, Irrigation, Law, and Legislative Affairs of the newly created state of Uttaranchal. In 2001 he replaced Nityanand Swami as the chief minister of Uttarakhand. He has also served as the President of the BJP of his state. As a result of his party's defeat in the 2002 Assembly elections, he resigned in March 2002 as the chief minister. However, he was elected from Kapkot assembly constituency, and became the leader of the opposition of the Uttarakhand Legislative Assembly, till 2007.
In the 2007 Assembly elections in Uttarakhand, he was elected again from Kapkot assembly constituency. However, despite the BJP's victory, Koshyari was deprived of the Chief Minister's post by his chief rival, Bhuwan Chandra Khanduri. Media reports have cited that the BJP's central leadership was biased for Bhuwan Chandra Khanduri, despite his support from the RSS and a majority of the elected MLAs. In November 2008 he was elected a member of the Rajya Sabha from Uttarakhand and remained a member till his election to the Lok Sabha in 2014. He has been appointed a national vice president of BJP and also BJP chief in Uttarakhand .
In the 2014 Indian general election, he was elected to the 16th Lok Sabha from Nainital-Udhamsingh Nagar, Lok Sabha constituency.
He founded various schools in Uttarakhand (Saraswati Shishu Mandir, Pithoragarh, Vivekanand Vidya Mandir Inter College, Pithoragarh; and Saraswati Vihar Higher Secondary School, Nainital).