The much-anticipated feature was first spotted by WABetaInfo, who revealed that the animations are still under development, and explained that beta testers may not be able to see it even if they update the app to its latest version.
The animated stickers will be part of sticker packs, and when rolled out, third-party animated packs could also be used.
The messaging service - which is owned by Facebook - previously announced it was releasing packs created by its own designers and a number of outside creators to supplement GIFs and emojis within the app.
To use the stickers, users will simply tap the new button and choose which one to send.
The company announced in a blog: "Whether with a smiling teacup or a crying broken heart, stickers help you share your feelings in a way that you can't always express with words."
WhatsApp urged other artists to make more stickers for use in the app, and to do that they released a set of interfaces and APIs to allow people to create third-party packs which can be added to the initial selections via both the Google Play Store and Apple's App Store.
The company confirmed: "Stickers will be available for Android and iPhone over the coming weeks. We hope you enjoy them!"