Wish your sister a very happy 20th birthday with these great wishes. You can also use them to surprise the birthday girl with a poem, a personalized message or anything else you can think of. She’s been there for you when you were growing up and she’s always been there for you with all your problems. Now it’s the time to return the favor by wishing her a very happy 20th birthday.

Happy 20th Birthday Wishes For Sister

1. On your birthday I just want you to know that you are smart, funny and a great friend. You had a big heart, and there was nothing that you wouldn’t do for anyone that needed help. But somehow in each conversation our talk always came back around to boys. You have always been a great person who can make anything feel like a party. So I want you to celebrate your 20th with all the fun that you deserve! Happy birthday sister!
2. Well, you’re another year older – but that’s only ‘cos you don’t know the date. HAPPY 20TH BIRTHDAY SISTER! I love you to little pieces, you are my one and only sister, and also my best friend. You have been there for me through everything I have ever done, and believe me I have done A LOT! We have had our ups and downs over the years, but we always get back to each other.
3. It is hard to believe that you are 20 years old today. Time has been flying by and before I know it you will be 30. Happy Birthday my sister!
4. To my sister on your twentieth birthday: A promise to be the best sister I can be, to always take care of you and love you more than you can imagine. This day is for you and for making new memories. I hope it will be filled with happiness and hope.
5. I’ve loved you for so long and now it’s your 20th birthday, I am reminded of just how much. As a kid, we used to be inseparable and even as adults we can’t go a day without talking, laughing or texting. You are my best friend, my rock and most importantly, my sister. Happy birthday, my love!
6. It’s hard to believe you’re 20. When I look at you, I still see the tiny child that followed me around. Now I’m the one who follows you around! 🙂 Gross, I know! Ha ha! But seriously, I am thankful for our bond, and I hope you never change. My beautiful baby sister.
7. You have been my sister for as long as I can remember. I have always looked up to you and the person you have become. You’re smart, kind, and beautiful, but most importantly, you are my best friend. Happy 20th birthday!
8. I cannot tell you how proud I am of you. You have come so far and have accomplished so much in just 20 years. I hope each day is as great a joy as it can possibly be. I love you more than anything in this world, happy Birthday sister!
9. Firstly, happy 20th birthday and thanks for being such a great sister. I want to thank all of you for being such an awesome sister, friend, confidante and mother figure all at once! Give yourself a pat on the back. Life is good.
10. You’re just like a sister to me. I’m so proud of you and the things you’ve accomplished over the past 20 years. Never stop dreaming because you have such a bright future ahead of you! Happy 20th Birthday sis.
11. Congrats sis! Happy 20th Birthday sis. We have come a long way haven’t we? And as much as I’ve enjoyed every moment of having you as my sister I just want to let you know that it’s been an even greater joy watching you grow and become the awesome, kind and beautiful person you are today. You really deserve the best and I hope you get everything your heart desires. I love you sis, because you’re mine…and nobody else is allowed.
12. I could tell you about how I’m in awe of your growth into a young woman, or how I’m proud to have seen you through your 20 years on this planet. I could tell you how you inspired me to raise my own children with the same values and morals that you hold dear. Or I could tell you any number of things that most people wish they could say to their siblings as they commemorate a milestone like this one. Happy 20th Birthday sis.
13. Happy Birthday dear sister! I hope this year will bring you many wonderful surprises. Enjoy your 20years birthday, it’s the best time of your life!
14. Happy 20th birthday sis. It’s hard to believe that you’re 20 already. You have grown up so much in the last few years and I’m so proud to be your sister. Have a great day!
15. Happy 20th birthday to my dearest sweet and amazing little sister. You’re not a little girl anymore, you are an amazing woman. I want to wish you the happiest birthday ever! I hope you get everything on your wish list, but most of all, I hope you get to see how loved you are by your family and friends. You deserve all the best!
16. I couldn’t ask for a better sister, even though you are younger. I remember when we were little I would come to you for advice and listen to every word you said because I knew it was going to be the truth. You are so funny, caring, and unbelievably smart. I admire your sense of humor and outlook on things. You make me smile, laugh and worry about being your big sister. I’m so happy that now you will be 20 just like me!
17. Happy 20th Birthday sis. You make me feel like the luckiest person on earth. You are the greatest sister in the world. I love you and cherish you….
18. Happy Birthday sis. I can’t believe you are turning twenty. You have been such a huge part of my life that I feel like we have grown up together. Here’s hoping you continue to grow up and become whoever you want to be when you’re older. Love you!
19. Happy 20th Birthday Sister.  You’re my best friend, the greatest person I know. I hope to keep you around for at least another 20 years! Happy birthday!  Hope you like the gift.
20. Happy 20th Birthday sis. You are the best friend, sister and daughter a person could ask for. You put others first all the time and I admire you for that. You are very caring and thoughtful, always putting other’s feelings before your own. Do not ever change who you are and continue to be sweet, adorable and silly!
21. I love you more than I have ever loved anything in my life. It means so much to me that you are my sister. And as silly as it sounds, knowing that you will always be there for me makes dealing with the struggles of life a lot easier. Thanks for being an amazing sister! Happy 20th Birthday sis.
22. Happy 20th Birthday sis. I am so happy that you were born. I feel so lucky to have a sister like you. I love how funny and sensitive you are. Plus you are very pretty in general. I hope your day is filled with whacky fun and memorable moments.
23. I write this letter to express how grateful I am that we were born only seconds apart. You have always been there for me, for any little thing that came up you were right there to help out. You mean the world to me, your happiness means my happiness, and everything I do is to try and make you smile. I can’t tell you enough how lucky I feel to have a sister like you and how thankful I am that we are celebrating our 20th birthday on the same day.
24. Happy 20th Birthday sis. To the most important person to me, my little sister. We’ve been through a lot together and I just want you to know that I love you and I’m proud to be your big sister. You mean the world to me and I couldn’t imagine my life without you. Years from now, when we look back at these birthday wishes for sister, I hope we will always remember the good times we had together and the great times yet to come.
25. You may be the youngest but you are one of a kind. Your heart is as pure as gold, I’ve yet to meet someone like you. You’re so full of life, your infectious personality is welcoming to all. I am so proud of the woman you are becoming; 20 years old may seem young but to me you are all grown up and ready for the future, I look forward to seeing how wonderful you will become in the next 20 years.
26. Hey little sis, I’m so glad to have you as a sister. Happy 20th birthday to you. As you turn into the next phase of your life I hope that you never forget how awesome you are. You are smart and funny, loyal and caring but most of all beautiful.
27. I love you so much! It has been an incredible 20 years. I’m so blessed to have a sister like you in my life, someone I can share my heart with, be silly with, talk and laugh with. You’re not just my sister, you’re my best friend.
28. Happy 20th Birthday to my Sister, I hope you are having the best birthday ever. You deserve it and so much more! Life is full of twists and turns, but as long as I have you in my life I can do anything! I love you, have a great day!
29. Happy 20th birthday to my amazing little sister! Our relationship has had it’s ups and downs, but you are always there when I need you. You are always messing with me and getting on my nerves. However, I just can’t get rid of you. I love you so much and wish only the best for your future.
30. Happy 20th birthday to the best little sister a guy could have! You are such an amazing person and I have so much love for you.
31. I can’t believe you are already twenty. I feel like yesterday you were five, running around pushing me on the swings and trying to knock the ice cream off my cone. Now here you are …twenty! So grown up and out of the house. Now that I think about it, you were 20 once, just younger! I love watching you grow and see how much in life you have to look forward to.
32. I know you’d never admit it, but you’re my best friend too. I can always tell you anything without fear of judgment. Even though we’re thousands of miles away, I still feel like we’re right next door to each other. You are so much to me and I’ll always be there for you. No matter where life takes us we will always be sisters! Happy 20th Birthday.
33. Happy 20th birthday sis. You taught me how to walk, how to talk, how to be a woman. You showed me right from wrong and that hard work pays off. You were always there when I needed you. There are no words to express how much joy you have brought into my life. I love you so much!
34. Happy 20th Birthday sis. You are a wonderful sister, I could not ask for better. I love how hard you work at your studies and how much you care about other people. You are my closest friend and I’m so lucky to have a sister such as you. You make me proud every day!