Short answer
No, not all of them. Jinn are a creation with free will, like humans: some are Muslims and righteous, others disbelieve and do harm. The evil ones are called shayatin (devils). Believers should not live in fear of jinn, but should seek Allah's protection from their harm.
Belief that jinn exist is required, since the Quran affirms them; denying them outright is denying the Quran. Jinn are accountable (mukallaf) like humans, rewarded for faith and punished for disbelief.
The four schools agree on this.
Explanation
The Quran says Allah created the jinn from a smokeless flame of fire and created them, like humans, to worship Him (51:56). Surah al-Jinn records a group of jinn who heard the Quran and believed. They said, "Among us are the righteous, and among us are others not so" and "among us are Muslims, and among us are the unjust".
So jinn are not a race of demons. They eat, marry, have children, die and will be judged. Muslim jinn pray and fear Allah. The disbelieving and rebellious ones follow Iblis, and they whisper, frighten and sometimes harm people by Allah's permission. The Prophet ﷺ said every person has a qareen (companion) from the jinn assigned to him, which is why constant dhikr matters.
Protection is simple and in your hands. Say bismillah when entering the home, eating and undressing. Read ayat al-kursi before sleep, and the last two surahs of the Quran morning and evening. Keep up the five prayers. The jinn have no power over a heart that remembers Allah, and fear of them should never be greater than trust in Allah.
Two warnings. Do not seek help from jinn, fortune tellers or anyone who claims to command jinn, as this leads to shirk. And not every problem is a jinn: mainstream Sunni scholars accept that jinn can harm and even possess a person, but most symptoms people blame on jinn have medical causes, so see a doctor as well as using ruqyah from the Quran. More in Jinn in Islam.
The evidence
Quran, Surah Al-Jinn 72:11
وَأَنَّا مِنَّا ٱلصَّٰلِحُونَ وَمِنَّا دُونَ ذَٰلِكَ ۖ كُنَّا طَرَآئِقَ قِدَدًۭا ﴿١١﴾
And among us are the righteous, and among us are [others] not so; we were [of] divided ways.
The jinn themselves say some of them are righteous and some are not.
Quran, Surah Al-Jinn 72:14
وَأَنَّا مِنَّا ٱلْمُسْلِمُونَ وَمِنَّا ٱلْقَٰسِطُونَ ۖ فَمَنْ أَسْلَمَ فَأُو۟لَٰٓئِكَ تَحَرَّوْا۟ رَشَدًۭا ﴿١٤﴾
And among us are Muslims [in submission to Allah], and among us are the unjust. And whoever has become Muslim - those have sought out the right course.
Some jinn are Muslims.
Quran, Surah Adh-Dhaariyat 51:56
وَمَا خَلَقْتُ ٱلْجِنَّ وَٱلْإِنسَ إِلَّا لِيَعْبُدُونِ ﴿٥٦﴾
And I did not create the jinn and mankind except to worship Me.
Jinn are created to worship Allah and are accountable like humans.
Quran, Surah Ar-Rahmaan 55:15
وَخَلَقَ ٱلْجَآنَّ مِن مَّارِجٍۢ مِّن نَّارٍۢ ﴿١٥﴾
And He created the jinn from a smokeless flame of fire.
States what the jinn are made from.
Sahih Muslim 2814
Sahih... مَا مِنْكُمْ مِنْ أَحَدٍ إِلاَّ وَقَدْ وُكِّلَ بِهِ قَرِينُهُ مِنَ الْجِنِّ ...
"There is none of you except that his companion from the jinn has been assigned to him."
Shows the jinn's role in whispering and the need for protection.
Where the ruling is recorded
- Akam al-Marjan fi Ahkam al-Jann (al-Shibli al-Hanafi), Chapters on the jinn being accountable and on their believers. A Hanafi work that sets out that jinn are accountable and that some of them are believers.
This answer is pending review by the scholars on our team. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.