
Most people looking for condolences for loss of mother are holding a pen over a blank card and have been for a while. So here is the short version before anything else: I am so sorry about your mom. She raised someone wonderful. You can send that exactly as written. It is warm, it is specific enough to mean something, and it does not ask the person receiving it to do anything.
The rest of this page is fifty more, sorted by who you are writing to and how well you knew her, because that is the thing that actually changes the wording. There is also a short section on what not to write, and one on what to do after the card, which is the part nobody covers.
If you want the mechanics of the card itself โ structure, sign-off, what goes on the envelope โ our guide to what to write in a sympathy card covers that, and the is the starting point for every other relationship.
The nearest ones to this are worth naming, because people often need two at once when a family loses somebody: sympathy message for loss of father, condolence message for loss of brother, and sympathy message loss of child.
This is the most-searched version of the question by a wide margin, and it is the right instinct. A card with one true sentence in it lands better than a card with a paragraph of arranged phrases.
People type short sympathy for loss of mother and condolence messages loss of mother into a search bar interchangeably, and they want the same object: something that fits on the left-hand page of a card and does not sound like it came off a shelf. Any of the ten above will do that.
If the death was expected after a long illness, I am so glad she is not in pain, and so sorry she is gone is one of the few lines that acknowledges both halves honestly.

You have latitude here that a colleague does not. Use her name. Use a memory. Say the thing you would say out loud.
The strongest sympathy message for loss of mother from a close friend is almost always a memory rather than a sentiment, because a memory proves she was known. She taught me to drive in the grocery store parking lot does more work than a paragraph about strength and grace.
Warmer than a work email, cooler than the section above, and short. A colleague reading this at their desk on their first day back does not want to be undone by a card from the team.
Two rules for the professional register. Do not ask questions โ a card that asks how are you holding up? obliges a reply. And do not mention work in the same breath as the death; if cover needs arranging, that is a separate message.
Our page on condolence messages for a coworker goes further into the professional wording, including group cards and email.
Most people writing a card are in this position, and it is the case that produces the most anxious searching. You are not required to have known her. You are writing to the person, not about the mother.
That third one is worth keeping. I did not want to say nothing is honest, and it is the reason most people are searching at all.

Match the family's tradition, not your own. If you are unsure what the family believes, the secular options above are the safer choice โ a mismatched blessing reads as carelessness at exactly the wrong moment.
Christian
Jewish
Muslim
Non-religious but spiritual
May her memory be a blessing is the single most-used line in this whole category, and for good reason โ it is warm, it centers her rather than the loss, and it carries no theology anyone has to agree with.
One practical note on names. If you knew her, use the name you used for her โ Mrs. Alvarez, Dot, Grandma Ruth. If you did not, your mother is warmer in writing than your mom and never sounds presumptuous. And if the family used a different word than you would expect, follow theirs.

The medium changes the length, not the sentiment.
A card can hold three or four sentences and will be reread months later โ this is where a memory belongs. A text should be one or two lines and should not require an answer; no need to reply, just thinking of you is a complete message. In person, say less than you think. I am so sorry with eye contact beats anything longer.
For the digital version, what to say to someone who lost a loved one over text is mostly a question of timing and follow-up rather than wording โ send it when you think of them, and send another one later.
Choosing between them is a judgment about the relationship rather than about the death, and it is the part people get wrong most often โ a close friend sent an email reads as filed, a supplier sent a handwritten card reads as odd. How to offer condolences sets out which channel suits which relationship, and the sequence that follows the first message.
Every one of these is well-meant and every one of them lands badly.
The pattern is that comforting words loss of mother searches turn up a lot of phrases designed to close the subject. The good ones open it instead โ they say I am here and I am not in a hurry.
This is where most advice stops and where most of the help actually is.
The card arrives in the first week, when the house is full of casseroles and relatives. The hard part comes six weeks later when it empties, the phone stops, and everyone else's life resumes. Put the date in your calendar now, while you are thinking about it. Send a second message at a month, and again at the first birthday and the first Mother's Day โ those two are the days people brace for privately and nobody mentions.
The second message does not need new material. Thinking of you today. Still miss her is enough, and it will mean more in November than anything you wrote in September.
If you want to send something alongside the card, bereavement gifts that do not need tending are the safest choice โ a grieving household does not need another thing to water. Our guide to sympathy gifts for the loss of a parent walks through what suits.

A keepsake like these is a good first gift because it asks nothing of the person receiving it. The order of service, the hospital bracelet, the last card she sent โ those things need somewhere to go, and for the first few months a drawer is where they end up.
For something meant to be kept rather than consumed, memorial gifts for loss hold a photograph, a name, or a date.

Later still โ and this is months away, not weeks โ some families choose an engraved keepsake or a line for a marker. Our page on headstone inscriptions for a mom exists for that stage, and it is worth knowing it is there before anyone asks you for a suggestion.
What do you say when someone's mother dies? Say that you are sorry, and say one specific thing about her or about them. I am so sorry about your mom. She was so proud of you. Two sentences is a complete message.
Is it too late to send a card? No. Cards arriving at six weeks or six months are often the ones people remember, because everyone else has moved on. Open with I have been thinking about you since your mom died rather than apologizing for the delay.
What should I write if I did not know their mother? Write to the person, not about her. I never met your mom, but I have met you, and that tells me a lot about her is honest and complete.
Should I mention how she died? Only if the family has. Never name a cause of death in a card, and never ask. If they raise it, follow where they take it and no further.
Do I sign it from just me or from the whole household? Either is fine. If your family knew her as a family, sign it that way โ it tells the reader how widely she was known, which is its own kind of comfort.
What is the best short message? I am so sorry about your mom. It is the most-used line in this category because it is the one nobody regrets sending.
There is no wording that makes this better, and looking for one is why the pen has been hovering. The card does not have to fix anything. It only has to say I know what happened, I am thinking of you, and I am not going anywhere โ and almost any honest sentence will carry that.
Pick one from the top of this page, write it in your own handwriting, and send it today rather than perfecting it.