40th Birthday Messages for Sister: What to Write in the Card

October 7, 2026

You're in the right place for 40th birthday messages for your sister. There are 12 ready-to-copy lines on this page, grouped into short 40th birthday messages for your sister, heartfelt 40th birthday messages for your sister and funny 40th birthday messages for your sister, plus more below - pick one, change a detail so it sounds like you, and you're done.

Quick answer: start with "Happy 40th, sis!", add one line about what they mean to you or a memory you share, then finish with a wish for the year ahead. Sign off with "Love you, sis".

A 40th birthday is a big one, so a card for your sister deserves a bit more thought than "have a good one". The messages below are grouped by tone so you can copy one straight in or mix a funny line with a sincere one, which is the combination that usually lands best.

Short 40th birthday messages for your sister

Happy 40th, sis! Have the best day.
Happy 40th birthday, sis. Here's to you.
Forty is the new thirty. Ask anyone who's forty.

Heartfelt 40th birthday messages for your sister

Happy 40th, sis. You're my first friend and my forever one.
Happy 40th, sis. Thank you for always picking up the phone, whatever the hour.
40th years, and you've made every one of them count. Happy birthday.

Funny 40th birthday messages for your sister

Happy birthday to my sister. Mum's favourite, I'll admit it just this once.
I've known you longer than anyone and I still like you. That's a gift in itself.
Life begins at 40. The back pain starts at 41.

40th birthday gift ideas for your sister

A spa day together
A personalised star map or print
Matching sister jewellery

How to write it so it lands

Mix one joke with one sincere line.
Mention a specific memory: it's the line they'll reread.
Add a photo inside the card for a milestone.

Frequently asked questions

What do you write in a 40th birthday card for your sister?

Happy 40th with their name, one personal line about what they mean to you, and a wish for the year ahead.

What is a short 40th birthday message for a sister?

"Happy 40th, sis! Have the best day." Short is fine if it sounds like you.

How should I sign a 40th birthday card to my sister?

Love you, sis.

What is a good example of 40th birthday messages for your sister?

"Happy 40th, sis! Have the best day." is one of 12 examples on this page. Pick the one closest to the tone you want, then add a specific detail of your own - a shared memory, a date, a name - so it reads as yours rather than copied.

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