"Hold tight, folks! Signal is currently down, due to a hosting outage affecting parts of our service. We're working on bringing it back up," the firm said in a tweet on Sunday.
The status website says the encrypted messaging app is "experiencing technical difficulties" and many people are also getting an in-app error message that says the same thing.
Signal allows for secure and encrypted video, voice and text communication, but users are unable to send any messages.
According to Downdetector.com, users started reporting outages around 11:05 PM Eastern Standard Time and it appears to be affecting people around the world.
Comments shared on Downdetector.com indicates that Signal was down for users from India, US, Germany, New Zealand, Netherlands, Australia, Brazil and many other countries.
"Down in Midwest USA. Signal was started by people connected to which secret 3-letter organization? (Look it up) Yep, that's right! An app disguised a privacy app to trick you into sharing more private information than you would with another messaging app," a user said.
"I think Signal is having a rough day. Good luck, Team Signal. I'm sure you'll have it sorted out in a snap," said another.
The encrypted messaging service has climbed to the top spot in the free apps category of the App Store in multiple countries, including India.