A five-member bench of the country's apex court unanimously ruled on Friday that anyone disqualified under a constitutional clause requiring legislators to be "honest and trustworthy" would be considered banned for life.
Sharif was dismissed from office as prime minister in July 2017, in a case lodged over disclosures in the Panama Papers leak, but which ultimately hinged on allegations that he had failed to declare a salary from his son's UAE-based company, Al Jazeera reported.
Sharif says he never received the salary, and that he held a position within that company in order to maintain a valid business visa in the UAE. The court ruled that whether he received the salary or not was immaterial.
The three-time prime minister and three of his children continue to face trial for corruption charges in a National Accountability Bureau court, which is due to deliver a verdict in the coming weeks.
Sharif himself had twice been removed from office during previous stints in power in the 1990s, once after a tussle with the president and a second time in a military coup by former army chief Pervez Musharraf.
Pakistan is due to hold a general election in July.