In 1989, after graduating with honors from the Department of International Relations at the Shevchenko University in Kiev with a degree in international economics, Poroshenko pursued his masters.
From 1990 to 1991, Poroshenko was the deputy director of "Respublika" ("Republic") – an alliance of small enterprises. From 1991 to 1993, he was the head of the joint-stock association "Exchange house 'Ukraine'." Later he was the director of the closed joint-stock company "Ukrainian Industry-Investment Trust."
In the parliamentary elections of 1998, he was in the eleventh place in the party list of Social Democratic Party of Ukraine (united) (SDPU (u)). However, Poroshenko received his deputy mandate in the majority district number 12 (Vinnitsya district). Poroshenko was also a part of the parliamentary fraction the United Socio-Democrats and was a member of the Politburo. He explained his decision to join the Social Democrats as "Because SDPU is an opposition party. Because, in my view (although I’m not a member of the party), this is a party of pragmatics, a party of competent people."
In the beginning of 2002, Poroshenko left the SDPU and created his own leftist fraction "Solidarity" – later the "“Party of the Solidarity of Ukraine." The latter became a part of the Regions of Ukraine Party (RUP) in the fall of the same year. Poroshenko became the co-head of the said party and in March 2001 was made the deputy head of RUP – a position he left after six months.
In December 2001, the "Solidarity" party became a part of Victor Yuschenko’s electoral bloc "“Nasha Ukraina" or "Our Ukraine" and Poroshenko became the head of the bloc’s electoral headquarters.
Since May 2002, Poroshenko was the head of the Parliamentary Committee on Budgetary Issues and in July 2004, became the deputy head of the "Sila Naroda" or "The Power of the People" coalition headquarters.
On January 24, the President of Ukraine appointed Petr Poroshenko as the Secretary of National Security and Defense.