After completing his PhD, Joshi taught Physics at Allahabad University. He came in contact with the RSS in Delhi at a young age and took part in the Cow Protection Movement in 1953–54, in the Kumbh Kisan Andolan of UP in 1955, demanding halving of land revenue assessment.
During the Emergency, Joshi was jailed on 26 June 1975 until the Lok Sabha elections in 1977. He was elected Member of Parliament from Almora. When the Janata Party (which then included his party) came to power forming the first non-Congress government in India, Joshi was elected General Secretary of the Janata Parliamentary Party.
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After the fall of the government, his party quite the Janata Party in 1980, and formed the Bharatiya Janata Party or the BJP. Joshi first looked after the Central Office as a General Secretary and later became Party Treasurer. Later, when BJP formed the government under Atal Bihari Vajpayee in 1998, Joshi served as Human Resource Development Minister in the cabinet.
Joshi is known to have been influenced by the life and work of Veer Savarkar, Shri Guruji and Deendayal Upadhyaya. He was a three-term MP from Allahabad before he was defeated in the Lok Sabha elections of May 2004.
He won the election to the 15th Lok Sabha from Varanasi as a BJP candidate. He also served as the home minister for 13 days government in 1996. He was a sitting MP from Varanasi and vacated his seat for Narendra Modi.