CareerRao hailed from Buyannagudem in Khammam district. His involvement in politics began when he was in his twenties, when he supported Congress in their campaign of armed defiance against the Nizam of Hyderabad. He was jailed for his involvement in this campaign, which was protesting the tenancy laws operating in the Telangana region. Although he tried and failed to be elected as an independent candidate in 1952, Rao subsequently was elected on four occasions to the Legislative Assembly of Andhra Pradesh, where he represented the Sathupalli constituency of Khammam district. He was also twice elected to the Lok Sabha - the lower house of the Parliament of India - as a representative of the Khammam district constituency. The first of his successful Assembly elections was in 1962, and the period from 1952 to that time saw him occupying the post of president for the Khammam district branch of Congress and being the first chairman of the district council.
In 1968 he became State Home Minister in the Assembly government of Kasu Brahmananda Reddy. Later, during his period as Chief Minister of Andhra Pradesh, an office to which he was appointed by Indira Gandhi and held between 10 December 1973 and 6 March 1978, Rao's hallmark was his administrative efficiency. He is also known for his handling and containment of Naxalite insurgency, which took place during a revival of the Telangana movement that sought independent statehood. He replaced local officers with officers from far away districts so that a nexus between the Naxalites and the police could not be formed. He also introduced rehabilitation measures for the families of slain Naxalites so that they could lead an honourable life and not resort to the path of their forebears. He almost wiped out Naxalism from the state. He improved the lot of the tribals to ensure there were no fresh additions to the cadres. Later, the Vimadlal commission was appointed to probe into attacks on Naxalites during his period in office and his earlier actions against Communist-inspired Naxalites during the 1960s have been referred to as a "reign of terror". The official website for the government of Andhra Pradesh refers to his Chief Ministership, which came about following a period of President's rule, as a "popular ministry ... With this, normalcy returned and the State enjoyed political stability". Despite that popularity, he was unable to retain power in the 1978 elections.
When Congress split during the mid-1970s, Rao initially did not join with the faction led by Indira Gandhi that was referred to as Congress (I). However, he did join in 1984 and with his election to the Lok Sabha in that year he served in the cabinet of Rajiv Gandhi, holding the post of Union Minister for Industry until 1989. For much of this period, between 1984 and 1988, he was also president of the state organisation of his political party, being the Andhra Pradesh Congress Committee.
It was during his tenure as Chief Minister that three universities namely Kakatiya University, Acharya Nagarjuna University and Sri Krishnadevaraya University were started, catering for three regions of Andhra Pradesh: Telangana, Andhra and Rayalaseema. Rao initiated a World Telugu Conference in Hyderabad in 1975.
Jalagam Vengal Rao died on June 12, 1999. One of his children, Jalagam Venkat Rao, is also a politician and as of 2009 was a Member of the Legislative Assembly of Andhra Pradesh, representing the INC for the same constituency, Satthupalli, as his father.
CommemorationRao wrote an autobiography in the Telugu language, called Naa Jeevitha Katha. The contents caused some controversy with regard to the lives of other politicians.
A part of it was published in English translation by Outlook magazine.
A park in Banjara Hills, Hyderabad was named after him as Jalagam Vengal Rao Park. There is also an upscale residential neighbourhood named after him – Vengal Rao Nagar - and several educational institutions.