Is it sunnah to smile?

Yes, smiling is part of the Prophet's sunnah. He smiled often and met people with a cheerful face, and he taught that this kind of small kindness is good in itself. It is not a strict obligation, but it is a simple way to follow his example every day.

The Prophet ﷺ was known for his smile

One of the Companions said: "I have not seen anyone who smiled more than the Messenger of Allah" (Jami at-Tirmidhi 3641). Jarir ibn 'Abdullah said that since he accepted Islam, the Prophet ﷺ never turned him away and whenever he saw him, he received him with a smile (Sahih al-Bukhari 3035).

His wife 'A'ishah described his laughter: she never saw him laugh so heartily that his palate showed. He would simply smile (Sahih al-Bukhari 6092). A warm, gentle smile was his normal way of meeting people.

A cheerful face is a good deed

The Prophet ﷺ told Abu Dharr: "Don't consider anything insignificant out of good things, even if it is that you meet your brother with a cheerful countenance" (Sahih Muslim 2626). Many people think good deeds have to be big. This hadith says that something as small as a friendly face counts. Scholars connect it to the idea that kindness is part of faith, not an extra. The "charity" side of the hadith about smiling is explained separately. See Is a smile really charity in Islam?

Smiling and laughing in balance

The sunnah is a gentle smile, not constant loud laughter. The Prophet ﷺ said: "Do not laugh a lot, for laughing a lot deadens the heart" (Sunan Ibn Majah 4193). Islam doesn't ask you to be gloomy. Joking and happiness are fine, as long as they are honest and kind. See Is it haram to tell jokes?

Everyday ways to put it into practice

Neighbours and colleagues: a smile and a simple greeting in the corridor or lift.
Shops, buses and cafes: smile at the cashier or driver and say thank you.
The mosque: smiling at newcomers helps a new Muslim feel welcome from the first visit.
Family: a smile when you come home or when someone wakes up can lift the whole house.
Difficult moments: a gentle expression when someone is upset or frustrated can calm things down.
Non-Muslims: your smile is often the first impression of Islam they get.

When a smile isn't right

At a funeral or when someone is grieving: a calm, sympathetic expression is more suitable than a bright smile.
When you are sad or unwell: Islam doesn't ask you to fake happiness or hide your pain. A sincere smile is better than a forced one.
With the opposite gender: a polite, natural smile is fine. Avoid flirtatious looks, and keep the interaction professional.

Welcoming faces matter especially for people who feel new or nervous. See How do I make friends at the mosque as a new Muslim?

Key points

The Prophet ﷺ smiled often and met people cheerfully (Jami at-Tirmidhi 3641).
A cheerful face is a good deed not to be belittled (Sahih Muslim 2626).
Keep to a gentle smile; too much laughter dulls the heart (Sunan Ibn Majah 4193).
Be sincere, and choose the right expression for the moment.

Tip: Pick one person each day, such as a neighbour, a cashier or a colleague, and give them a real smile with a greeting. It takes a few seconds and costs nothing.