The deal was struck following talks between the two sides, with the DMK side being led by its Treasurer M K Stalin which held discussions with the Khader Mohideen-led IUML.
"It has been decided that IUML will contest from five seats. The constituencies (it will fight from) will be announced later after having discussions with other alliance parties," the agreement, signed by DMK President M Karunanidhi and Mohideen said.
The IUML, which was a constituent of the Dravida Munnetra Kazhagam (DMK)-led front in 2011, had contested three seats in the 2011 Assembly polls.
Congress, the other ally in the coalition, is yet to begin the seat-sharing talks.