The Facebook-owned app announced they are working out a few tweaks before launching the feature for everyone, but now beta users only on Android, not Apple's iOS, have been able to use the function - which reduces eye strain and reserves battery power.
This suggests that iOS beta users may get a testing period before they decided to allow everyone to benefit from the darker screen.
A spokesperson for the app said last week: "WhatsApp is continuing to work on the Dark Theme, improving the last details before the release.
"It is continuing to add new features for the Dark Theme before the release.
"For this reason, it's normal if you don't see [Dark Theme] in WhatsApp, as it is under development."