His political career began in the 1980s when he was elected to the Pakistani Senate. He served as the Federal Minister for Law, Justice and Parliamentary affairs, and also held the portfolio of the Federal Minister for Interior, under the Government of Prime Minister Muhammad Khan Junejo.
He moved up to Chairman of the Senate in 1988, and served his first term as President in 1993, following the resignation of Ghulam Ishaq Khan. as interim president, Sajjad was essentially a placeholder for the office until elections were completed. He would run in the election for President, but was defeated by Farooq Leghari. In 1997, Sajjad was again made interim President and stepped down upon the election of Muhammad Rafiq Tarar.
In 2002, Sajjad was accused of mis-use of government vehicles and phones, amounting to millions of rupees. He was ordered to pay a fine, but served no time in jail.Sajjad continues to serve in the Pakistani government.