Short answer
No. A Muslim should not be a godparent, because the role is a religious promise, made in the baptism, to raise the child in the Christian faith. Attending a relative's christening to keep family ties is allowed if you only sit respectfully and take no part in the rite, though many Hanafi muftis advise skipping the service and joining the family meal afterwards.
Taking a role in another religion's rite, such as making baptismal promises as a godparent, is haram, and affirming the creed in those promises would endanger one's faith. Being present without taking part, for a real family need, follows the ruling on entering a church: allowed with need, disliked without it.
The four schools agree on this.
Explanation
In most churches the godparents stand at the baptism and make promises on the child's behalf: to reject evil, to profess the Christian faith, and to help bring the child up in it. For a Muslim, saying those words would mean affirming the Trinity and the divinity of Jesus, and promising to raise a child in a faith they no longer hold. That is why scholars say no, however much the family means it as an honour.
You can still be a wonderful aunt, uncle or friend. Visit, give gifts on birthdays or at Eid, help when times are hard, and be there for the child throughout life. None of that needs a church role.
- The christening service: if you go, sit quietly. Do not kneel, recite prayers or creeds, take holy water or communion. Many families will understand if you come to the meal instead.
- Gifts: a general baby gift is fine; avoid religious items such as crosses or a christening Bible.
- Photos: being in family photos is no problem.
Explain it with love: ‘I love her and will always be there for her, but I cannot make those promises in church because of my own faith.’ The Quran tells a believer to accompany even parents of another faith with kindness in this world, while not following them in worship. See can Muslims go to church, attending a church wedding and is there baptism in Islam.
The evidence
Quran, Surah Al-Kaafiroon 109:6
لَكُمْ دِينُكُمْ وَلِىَ دِينِ ﴿٦﴾
For you is your religion, and for me is my religion."
Muslims do not take part in the rites of other religions.
Quran, Surah Luqman 31:15
وَإِن جَٰهَدَاكَ عَلَىٰٓ أَن تُشْرِكَ بِى مَا لَيْسَ لَكَ بِهِۦ عِلْمٌۭ فَلَا تُطِعْهُمَا ۖ وَصَاحِبْهُمَا فِى ٱلدُّنْيَا مَعْرُوفًۭا ۖ وَٱتَّبِعْ سَبِيلَ مَنْ أَنَابَ إِلَىَّ ۚ ثُمَّ إِلَىَّ مَرْجِعُكُمْ فَأُنَبِّئُكُم بِمَا كُنتُمْ تَعْمَلُونَ ﴿١٥﴾
But if they endeavor to make you associate with Me that of which you have no knowledge, do not obey them but accompany them in [this] world with appropriate kindness and follow the way of those who turn back to Me [in repentance]. Then to Me will be your return, and I will inform you about what you used to do.
Family ties stay warm even where faith differs.
Quran, Surah Al-Maaida 5:2
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ لَا تُحِلُّوا۟ شَعَٰٓئِرَ ٱللَّهِ وَلَا ٱلشَّهْرَ ٱلْحَرَامَ وَلَا ٱلْهَدْىَ وَلَا ٱلْقَلَٰٓئِدَ وَلَآ ءَآمِّينَ ٱلْبَيْتَ ٱلْحَرَامَ يَبْتَغُونَ فَضْلًۭا مِّن رَّبِّهِمْ وَرِضْوَٰنًۭا ۚ وَإِذَا حَلَلْتُمْ فَٱصْطَادُوا۟ ۚ وَلَا يَجْرِمَنَّكُمْ شَنَـَٔانُ قَوْمٍ أَن صَدُّوكُمْ عَنِ ٱلْمَسْجِدِ ٱلْحَرَامِ أَن تَعْتَدُوا۟ ۘ وَتَعَاوَنُوا۟ عَلَى ٱلْبِرِّ وَٱلتَّقْوَىٰ ۖ وَلَا تَعَاوَنُوا۟ عَلَى ٱلْإِثْمِ وَٱلْعُدْوَٰنِ ۚ وَٱتَّقُوا۟ ٱللَّهَ ۖ إِنَّ ٱللَّهَ شَدِيدُ ٱلْعِقَابِ ﴿٢﴾
O you who have believed, do not violate the rites of Allah or [the sanctity of] the sacred month or [neglect the marking of] the sacrificial animals and garlanding [them] or [violate the safety of] those coming to the Sacred House seeking bounty from their Lord and [His] approval. But when you come out of ihram, then [you may] hunt. And do not let the hatred of a people for having obstructed you from al-Masjid al-Haram lead you to transgress. And cooperate in righteousness and piety, but do not cooperate in sin and aggression. And fear Allah; indeed, Allah is severe in penalty.
A Muslim does not take on a religious duty in another faith.
Where the ruling is recorded
- al-Fatawa al-Hindiyya, Kitab al-Siyar, the chapter on the rulings of apostates. Affirming the creed of another religion endangers a Muslim's faith.
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.