Can a non muslim convert to Islam on the day of her wedding?

In the Name of Allah, the Most Gracious, the Most Merciful.

As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.

The reversion of a non-Muslim female to Islam will be valid any time, even before her marriage on condition she honestly and sincerely accepts Islam and the fundamental principles of Islam which are:

1.  Belief in Allah
2. Belief in the Messenger of Allah (Sallallahu Alaihi Wasallam)
3. Praying Salah 5 times a day
4. Belief in Jannah (paradise) and Jahannam (hell)
5. Fasting in the month of Ramadan
6. Giving Zakat once a year (if eligible)
7. Going for Hajj once in a life time. (if eligible)

If she did not honestly and sincerely accept Islam and did so only for marriage convenience without submitting to the fundamental principles of Islam, then her Islam is not valid.

If she says she sincerely and truly accepted Islam, use the opportunity to educate her further on Islam.

And Allah Ta’āla Knows Best

Abdullah Syed Sajid

Student Darul Iftaa
Houston, TX, USA 

Checked and Approved by,
Mufti Ebrahim Desai.