Polling stations opened at 8 am local time (04:30 GMT) and will continue for 10 hours, but the interior ministry can extend the voting period depending on the voter participation rate.
90 candidates, who failed to receive an absolute majority of more than 50 percent of votes during the first round held on March 1, are running for the remaining seats.
The result will shape the trajectory of a myriad of issues facing the new parliament.
In the capital Tehran, whose lawmakers have historically played a key role in shaping Iran’s political landscape, 16 remaining seats are up for grabs.
Over 61 million people from Iran’s 85 million-strong population were eligible to vote on March 1 to choose the new members for the 290-seat parliament for a 4-year term.
In the first round of the election, the participation rate was around 41 percent, or 25 million people.
