Almost. It's a multi-ethnic country.
Ethnic Persians (Farsi) are only 60% of the population. There are some differing numbers for the rest, but Azeris (a Turkic people) are 16-20%, Kurds at least 10%, and there plenty more: Baluchis, Lurs, Mazandaranis, Semnanis, Turkmen, Arabs...
The diverse makeup, and having only ~60% being faithful Muslims (*), is a big part of the reason why it was always a difficult country to govern.
(*) going by Western surveys. There are a lot of atheists and agnostics, and some Zoroastrians, Christians ans Jews.
The regime claims 99.4% are Muslim which is bullshit.