The league is contested by 18 teams who competing for promotion to the 2010–11 Ekstraklasa. The regular season was played in a round-robin tournament. The champions and runners-up would receive promotion. Unlike in previous seasons the third-placed team no longer had the opportunity to compete in playoffs for promotion, while the 13th and 14th placed teams no longer had to compete in play-outs to remain in the I liga. The bottom four teams were automatically demoted to the II liga.
The season began on 1 August 2009, and concluded on 9 June 2010. After the 19th matchday the league will be on winter break between 22 November 2009 and 5 March 2010.[4]
Widzew Łódź won the I liga in 2008-09 but were relegated for prior corruption, hence remaining in the league.[5] Initially, they were also docked six points, however, this decision was overturned in September.[6]
Motor Lublin replaced GKS Jastrzębie who were not successful in their application for a license to play in the league.[7]
ŁKS Łódź, although not deserving it sportingly, were also relegated from the Ekstraklasa due to license problems.