Reports by affected users peaked at over 1,300 reports late Sunday, according to outage tracking website Downdetector.com.
About 43% of the issues reported were with its app, while 36% was with sending messages and 21% with its server connection, according to Downdetector.
The outage affected users around the globe, including the United States, Australia, and Germany, according to user complaints posted on Downdetector, while the outage map on the website showed concentration of complaints in the United States.
Signal did not immediately respond to a request for comment on the regions affected by the outage.
The messaging app said in a tweet earlier on Monday, "Signal is currently down, due to a hosting outage affecting parts of our service."
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.
Down Detector graph showing Signal app service outage.
In January, Signal experienced technical difficulties after rival messaging app WhatsApp announced a controversial change in privacy terms. Along with another rival Telegram, the company has been the main beneficiary of online outrage around WhatsApp's policy changes.
According to Downdetector, Robinhood, Reddit, Google's Nest and Tinder were also facing issues but it was unclear whether it was related to the same hosting outage.