How to Write an ‘Open When’ Letter for Your Sister


The bond with a sister is one of the strongest on earth. These siblings are lifelong friends, but sometimes life gets in the way. If you’re separated from your sister for any reason, or you’d like to do something extra special, an ‘Open When’ letter is a great idea. 

Jump ahead to these sections:

Gifting something that your sister can open on special occasions strengthens your bond and reminds her that you’re always there. Prepare for all of life’s moments by writing some ‘Open When’ letters for this special someone. Not sure how to get started? This guide makes it simple. 

What is an ‘Open When’ Letter?

To start, let’s define exactly what an ‘Open When’ letter is. This is a series of letters given to someone with the intention of them being opened at a later date. For example, you might have a letter to be opened on a holiday or on the recipient’s birthday. 

Why gift ‘Open When’ letters? If you’re separated from a loved one for a period of time, this is a way to make sure they have something special to look forward to. Offering kind words from a loved one in critical moments is a form of comfort. If your sister is moving away or you know you won’t be around, writing a series of ‘Open When’ letters ensures you’re always there for her. This small act of kindness can make someone’s day

» MORE: Online obituary that is 100% free. Honor a loved one beyond a newspaper.

How to Write an ‘Open When’ Letter to Your Sister

You don’t need any writing or crafting experience to get started. You can customize these ‘Open When’ letters as much or as little as you’d like. Here are some steps to get started. 

1. Plan your letters

Before you start writing, plan your letters. When do you want your sister to open these letters? It might help to look at a calendar of special dates and holidays to ensure you’re not missing anything. If you plan to have ‘Open When’ letters for important holidays or life events, here are some common options for a sister:

  • Holidays
  • Wedding day
  • Birthday
  • Birth of a child
  • Vacation
  • Moving day

Alternatively, you might choose something a bit more flexible. Another popular idea is to have ‘Open When’ letters for her emotions. These would be along the lines of open when you are stressed or open when you’re feeling homesick. No matter what you choose, your sister is guaranteed to feel less alone. 

2. Create a container

You’ll need some kind of container to hold all of your ‘Open When’ letters for your sister. Because you might have quite a few, you don’t want them to get lost. This is when you have the opportunity to get a bit creative.

Here are some ideas:

  • Shoebox
  • Jewelry holder
  • Taped within a planner
  • In the pages of a journal
  • Large envelope

Feel free to decorate your container to your sister however you wish. You might use paper, tape, paint, or just markers to create something that reflects your message. 

3. Write your letters

Next, it’s time to write your letters. You’ll find message inspiration below, but feel free to make these as formal or as casual as you want. It’s important that you write in your own words, so avoid taking too much wording from online. 

Consider the timing behind each ‘Open When’ letter. What would you say if you were there with her at this moment? How would you react in her footsteps, and what can you say to offer help? A lot of times, the best form of help is simply kind words and empathy. This is the time to strengthen your bond, so include stories, personal experiences, and inside jokes. 

It could also be fun to include small gifts, when appropriate, in some of the letters. Things like gift cards, photos, and digital downloads make perfect additions to your ‘Open When’ letters. 

4. Label each envelope

Finally, be sure to label each envelope clearly. You’ll want it to be obvious when each card should be opened. This is another opportunity to be creative with photos, drawings, calligraphy, and colors. 

From there, organize your envelopes in your storage container. Wrap it or leave it as is, and gift it to your sister. This makes the perfect going away gift, but it’s also a special memento for any occasion. 

» MORE: An online memorial is a perfect ending to honor and celebrate someone's life. Create one for free.

‘Open When’ Letter to a Sister Message Ideas

Need some inspiration for your ‘Open When’ letters for your sister? We’ve got you covered. There are so many milestones and occasions to choose from, so consider what applies most to your sister. 

1. Birthday

Spending a birthday apart from one’s family is difficult, especially for sisters who are used to doing everything together. Share a special birthday message for your first big day apart. This is perfect when paired with a small gift, favorite memory, or another message that brings a smile to their face. 

2. Wedding day

‘Open on your wedding day’ letters are very common, especially with sisters. Even if you can be there on their big day, having a letter they can open in private is a beautiful tradition. 

3. Pep talk

We could all use a pep talk from time to time. Having a pep talk in an envelope lets your sister take your kind words of advice on the go, wherever her life takes her. 

4. Graduation

Graduating is a huge milestone. If you can’t be there for any reason, let her know that you’re thinking of her during this huge accomplishment. 

» MORE: Grief can be lonely. Create space for your community to share memories and tributes with a free online memorial from Cake.

5. Homesick

Everyone experiences homesickness in some form. Whether she’s moving away or going on a long trip away from home, help here through these feelings with sisterly words of wisdom. 

6. Feeling sad

A sister is someone you go to when you’re sad. When you’re separated, having an ‘Open When’ letter to turn to offers a bit of sunshine on a rainy day. This is a chance to remind her why she’s important to you.

7. Missing you

Open when you miss me’ is a cute way to remember the good times you’ve had, and to also look forward to the future. Hearing a loved one’s words when you wish they were here is the best medicine. 

8. Laugh 

Sometimes you just need to laugh it out. Creating a letter that’s meant to put a smile on her face makes every bad day a little bit better. Bring out the inside jokes, hilarious memories, and anything else you know will brighten her day. 

‘Open When’ Letter to a Sister Letter Examples

For even more inspiration, these examples help you recognize why these letters are so powerful. Having your loved one’s words with you is a form of comfort no matter what life throws at you. 

Pep talk

So you need a pep talk? I know life can be hard sometimes. I want you to remember that you’re special to me, and you should always feel confident in yourself. You’ve got this, and you’ve always known what you want. This is no different. As the hardest working person I know, I already know you’ve got this figured out. I’m always here for you. 

Wedding day

I can’t believe this big day is already here. I remember when we were kids playing out in the yard together. The days really flew by, right? Today is all about you, sister. I’m so proud of who you’ve become, and I can’t wait to be there for you today. This is a huge chapter you’re about to embark on with your special someone. Just know that I’ll always be there if you need anything, now and forever. 


It’s okay to be homesick. I never told you about my first semester in college, but I was homesick every day. I wanted to pick up the phone and call you, but I was too embarrassed. I cried more than I’d ever like to admit! It was so hard being away from home, so I know exactly how you feel. Just know that this will pass. In the meantime, cuddle up with your favorite movie (how about one of our movie night favorites?) and a sweet treat. You can always pick up the phone and call me. Love you, sister!

Always Be There for Her

An ‘Open When’ letter is the best way to always be there for her. You don’t need to create anything fancy or extravagant to get your feelings across. If you’re hoping to do something special for your sister, a series of ‘Open When’ letters reminds her that she’s always in your thoughts, no matter how much distance separates you two. 

This idea not only makes the perfect memento or time capsule idea, but it warms her heart when she needs it most. Though simple, don’t underestimate the power of well-timed words. 

Icons sourced from FlatIcon.