After completing his law studies he decided to enter politics from his home constituency Kahror Pakka. In the 1977 general elections, he ran for the Provisional Assembly seat, but the elections were postponed. Again in 1985 he became Member of the National Assembly on non-party election, and served as a Parliamentary Secretary for Agriculture. The government was dissolved in 1988 and he was appointed as a caretaker Education Minister. During the first Benazir Bhutto government, Kanju for the first time became a part of the opposition headed by Nawaz Sharif. In the general elections of 1990, Kanju was for the third time elected Member of National Assembly from Lodhran, and at the behest of his friend and mentor Hamid Raza Gilani, joined the Nawaz Sharif cabinet as Minister of State for Foreign Affairs. During this period in 1991 he got changed Lodhran's status to a district, which was a tehsil of Multan District. In the General Elections of 1993, Kanju who was perceived as a success of the Muslim League, lost his National Assembly seat from Lodhran district. Jang reported his failure was due to extensive travel made as Minister of State and absence from the constituency. During the period 1993-1996 Kanju spent most of his time in Lodhran. He was again elected Member of National Assembly on Muslim League ticket. Once again he became part of Muhammad Nawaz Sharif's Cabinet, as Minister of State for Foreign Affairs, and served in this capacity until the Muslim League Government was dissolved by the military coup of 1999. When Mian Nawaz Sharif left the country, Siddiq Kanju with his group of members joined the new faction of Muslim League headed by Chaudry Shujjat Hussain, former Interior Minister under Nawaz Sharif, and Mian Azhar who was a former Governor of Punjab. During the local government elections of 2001, once again Kanju actively started campaign in his constituency. On 28 July when he was visiting a Counsellor shop in Kahror Pakka city, he was shot dead by three or four assassins along with MajorMuhammad Aslam Khan Joiya, ex MPA. One of his party workers were also shot. The place where Kanju died was the same where he gave his maiden speech as an incumbent in 1977 and started his career in politics. Siddiq Kanju died at the age of 49 years. His burial was attended by thousands of people. People from all walks of life condemned this act, and President Musharraf responded by saying it was a big loss. Interior Minister Moin-u-din Haider and Governor Sind, later Chairman Senate, acting Prime Minister and President Muhammad Mian Soomro took special notice and directed IG Punjab to take strict action. Two assassins were arrested by the police later in 2002.
