Short answer
Yes. A Christian, Jewish or other non-Muslim woman may wear a hijab, for modesty, out of respect when visiting a mosque, or to see what it feels like. Muslims generally welcome it. It is not a sin for her and it does not make her a Muslim; only the shahadah does that.
Islamic law does not oblige a non-Muslim woman to wear hijab, and nothing in it stops her from covering. Covering is modest and good in itself. What matters is the intention: wearing it to mock Muslims or as a costume would be wrong, but respect or curiosity is not.
The four schools agree on this.
Explanation
Covering the hair is not a new or purely Muslim idea. Mary, the mother of Jesus, is shown covered in Christian art, many Orthodox Jewish women cover their hair, and nuns and many church traditions still do. So a Christian or Jewish woman who wears a headscarf is close to the practice of her own tradition.
Common situations:
- Visiting a mosque: women are asked to cover their hair inside the prayer hall. Wearing a scarf there is good manners and most mosques keep spare scarves.
- Solidarity or curiosity: some women try hijab for a day to understand their Muslim friends. That is fine, and many Muslims are glad of it.
- Modesty: some non-Muslim women prefer to cover for their own reasons. Nothing in Islam objects.
- Fashion or a costume: wearing it to make fun of Muslims would hurt people and is wrong.
Wearing hijab does not make anyone a Muslim, and no one becomes Muslim by an outward act or by pressure. A person enters Islam by believing in one God and in His final messenger and saying the shahadah. The Prophet ﷺ taught that actions are judged by intentions, so a scarf worn with respect is a good act, while the scarf alone is not faith.
If you are wearing it because you feel drawn to Islam, you are welcome to learn more: see the shahadah and the new Muslim guide. To understand why Muslim women cover, read why Muslim women wear the hijab.
The evidence
Quran, Surah Al-Ahzaab 33:59
يَٰٓأَيُّهَا ٱلنَّبِىُّ قُل لِّأَزْوَٰجِكَ وَبَنَاتِكَ وَنِسَآءِ ٱلْمُؤْمِنِينَ يُدْنِينَ عَلَيْهِنَّ مِن جَلَٰبِيبِهِنَّ ۚ ذَٰلِكَ أَدْنَىٰٓ أَن يُعْرَفْنَ فَلَا يُؤْذَيْنَ ۗ وَكَانَ ٱللَّهُ غَفُورًۭا رَّحِيمًۭا ﴿٥٩﴾
O Prophet, tell your wives and your daughters and the women of the believers to bring down over themselves [part] of their outer garments. That is more suitable that they will be known and not be abused. And ever is Allah Forgiving and Merciful.
Gives the purpose of covering: modesty and protection from harassment.
Quran, Surah Al-Baqara 2:256
لَآ إِكْرَاهَ فِى ٱلدِّينِ ۖ قَد تَّبَيَّنَ ٱلرُّشْدُ مِنَ ٱلْغَىِّ ۚ فَمَن يَكْفُرْ بِٱلطَّٰغُوتِ وَيُؤْمِنۢ بِٱللَّهِ فَقَدِ ٱسْتَمْسَكَ بِٱلْعُرْوَةِ ٱلْوُثْقَىٰ لَا ٱنفِصَامَ لَهَا ۗ وَٱللَّهُ سَمِيعٌ عَلِيمٌ ﴿٢٥٦﴾
There shall be no compulsion in [acceptance of] the religion. The right course has become clear from the wrong. So whoever disbelieves in Taghut and believes in Allah has grasped the most trustworthy handhold with no break in it. And Allah is Hearing and Knowing.
No one becomes a Muslim by force or by an outward act alone.
Sahih al-Bukhari 1
Sahih... إنما الأعمال بالنيات وإنما لكل امرئ ما نوى ...
"Actions are only by intentions, and each person gets only what he intended."
The worth of wearing a scarf depends on why it is worn.
Where the ruling is recorded
- Radd al-Muhtar (Ibn Abidin), Kitab al-Jihad, chapter on the apostate (Bab al-Murtadd). Discusses what makes a person a Muslim in the eyes of the law: belief and the testimony of faith, not dress.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. 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.