21 Best Ways to Say ‘Happy Birthday’ to a Sister or Sister-in-Law

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No matter if the relationship with your sister is close or complicated. Full of fun or full of strife, it’s important to celebrate your sibling’s birthday. And, the least you could do is to send a text or post a message on social media. 

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Here are some ideas on how to say “happy birthday” to your sister or sister-in-law. Some of the messages are intended to be funny or even a little sarcastic. Other words will help you express how important your sister is to you. Some you may be able to use to pay tribute to a sister who died

Hopefully, these messages will give you inspiration on how to format the perfect message for your own sister. But remember, when it comes to talking with family members, it is best to speak from the heart. 

Funny ‘Happy Birthday’ Messages for a Sister

Most of the time, if you can be funny or sarcastic with your sister, that means you have a close relationship. Here are some somewhat-funny messages for your sister as she celebrates her special day. 

1. I smile because you are my sister. I laugh because there is nothing I can do about it. Happy birthday, sis!

“You can pick your friends, but you can’t pick your family.” Maybe a therapist said this to you once. Since you are stuck with them, you may as well figure out how to get along with them.

2. Happy birthday to mom’s second favorite daughter!

Of course, personalize this message, so it works for your situation. It is sure to get an eye roll from your sister when she reads it.

3. Sisters are a lot like sprinkles on top of an ice cream sundae. You can get by without them, but what would be the fun in that?

Who doesn’t love sprinkles? Exactly! Treat your sister as if she is your favorite ice cream topping.

4. Having a sister as awesome as me is the only present you need.

Your sister was probably going to return your gift anyway, so why bother? 

5. Happy birthday, sister! You look exactly the same . . . except older.

Do you have a sister who is worried about aging? Send her this message to tease her about it, and also buy her a bottle of Oil of Olay to accompany the birthday wish.

‘Happy Birthday’ Messages for a Big Sister

Older sisters are special, especially if they take the time to help you through life. Maybe your older sister was the one who taught you to put on makeup or drive a car. Perhaps she gave you advice on how to handle your parents or get through high school. 

It’s time to say birthday to your older sister. Here are some phrases to help you. 

6. Happy birthday, sister! When I was little, I looked up to you as my role model. Now that I’m older... nothing has changed.

Have you always looked up to your older sister? Let her know how much she means to you. Perhaps you are learning how to be a great mom or a wonderful grandmother from your older sister. 

7. Remember, no matter where you go or what you do, you will always be older than me. Happy birthday to my older sister!

Gently tease your sister about her age, if you think she can handle it. You may also consider finding poems about aging to share with a sister on a landmark birthday. 

8. Even though we are very different, we will still always be sisters. I love you dearly! Happy birthday!

Do you and your sister disagree about politics, religion, or child-rearing? Having a different worldview from your sister can put a strain on your relationship. Put those differences aside on her birthday, and let her know how important she is to you.

9. Happy birthday, sister! You are so smart, pretty, and vivacious (for your age.)

Are you the queen of back-handed compliments? Share this one with your sister on her birthday. She can’t get too mad at you for calling her old since you also called her “smart, pretty, and vivacious.”

10. Happy birthday sister, from the exact same mister!

You have heard of sisters from another mister. Here’s a way to celebrate the birthday of someone from your exact same genetic pool. 

‘Happy Birthday’ Messages for a Little Sister

It’s your little sister’s birthday! Even though you may think that she gets all the attention in the family, take time to send her a sweet birthday message. Here are some phrases to inspire you.

11. Happy birthday, little sister! You aren’t nearly as annoying as you used to be!

Let’s face it. No matter how close you are with your sister, she has annoyed you at times. Maybe she stole your clothes or told on you when you tried to sneak out of the house. Regardless of her past mistakes, it is time to let bygones be bygones and have a healthy, supportive relationship with your sis. 

12. Dear sister, I know there have been times when I have teased you, pestered you, and told on you. But I want to tell you that I think you are an amazing person. Happy birthday to the best little sister a girl could have. I love you!

Have you not been kind to your sister in the past? Take the high road and admit your mistakes. Make up for the past mistreatment by being kind to your sister now.

13. Happy birthday, sister! I know mom and dad were worried, but I guess you turned out all right in the end.

Are you looking for another back-handed compliment to wish your sister a happy birthday? Here’s one for the win. This is the perfect message for a sister who caused your parents strife during or teen years. 

14. Happy birthday, sister! I loved you yesterday, and I love you still. I always have, and I always will.

It’s important to tell others how we feel about them. In fact, maybe that should be a part of your birthday resolutions this year -- to say to others that you love them. Can you think of a better resolution than that?

15. With each passing year, you shine a little brighter! Happy birthday to my little sister!

Has your little sister grown up to be someone you look up to? Let her know! Chances are, she feels the same about you.

Short ‘Happy Birthday, Sister’ Messages for a Cake or Banner

Are you in charge of the cake or the banner for your sister’s birthday party? That’s quite the responsibility. Here are some messages that won’t get you in too much trouble from your mom.

16. One year closer to death!

We know this message may make people cringe, but it’s a tiny bit funny. Consider who will be around to read this cake or banner before committing to these words.

17. You are sweeter than this cake! Happy birthday!

Are you struggling to come up with a nice message for the cake besides, “happy birthday!”? This is a lovely, appropriate message to put on a cake.

18. Age is just a number. False: Age is a word.

Is your sister a fan of The Office? She probably has seen this meme that features the face of Dwight Schrute. If she’s not a fan of the show, this joke probably won’t work well.

19. We love you, (name)!

Purchase a customizable banner for your sister’s birthday. Not only could you use it for your sister’s birthday, but for other celebrations as well.

20. Blow out the candles before the fire alarm goes off!

Are there an awful lot of candles on your sister’s birthday cake? Why not tease her about it? 

21. Happy birthday, sister!

Why complicate matters? Simply wish your sister a happy birthday, and tell her that you love her.

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