The Taregh-1 joined the Iranian fleet in the southern port of Bandar Abbas after it was overhauled earlier this year, according to the TV report. It is one of three Russian Kilo-class submarines that Iran obtained in the early 1990s.
In May Iran redeployed another Russian-made submarine after repairs.
The report also showed the launch of what was said to be the partially completed hull of a destroyer, the Sahand, which the TV said is expected to be ready in the near future.
The announcement came two days after US-led naval exercises started in the Gulf. They are the largest such manoeuvres aimed at countering sea mines ever to take place in the region.