Persian World Outreach has recently completed a translation of Let the Nations Be Glad in Farsi, which you can order by emailing them.

We are very excited to see this book in Farsi, because it is the native language for millions, most of whom are Muslims who live in hard-to-reach areas like Iran and Afghanistan.

Persian World Outreach’s next Piper translation project is Fifty Reasons Why Jesus Came to Die, which should be available in the next year. They also offer many other English to Farsi translations (PDF).