"We are deeply concerned that our ads may have appeared alongside YouTube content promoting terrorism and hate," AT&T said in a statement provided to CNBC. "Until Google can ensure this won't happen again, we are removing our ads from Google's non-search platforms."
The suspension affects YouTube and Google's display network, according to The Wall Street Journal, which previously reported the news.
Verizon also told CNBC it pulled some ads from the platform after learning that they were appearing on "non-sanctioned" websites. Verizon said it wanted to make sure its brand was not negatively impacted and was investigating the "weak links" with advertising partners. Verizon said it's also pulling ads from other digital non-search properties, not just those owned by Google.
The telecom companies join other companies that have stepped back from Google, after an investigation from The Times of London found that ads for Mercedes-Benz and Marie Curie were running next to jihadist and neo-Nazi content.
Google apologized and revamped its ad policy on Tuesday, especially on YouTube. Google said it will start "removing ads more effectively from content that is attacking or harassing people," and will change the default safety setting for ads.
Google said on Wednesday that it couldn't comment on AT&T, citing a policy against commenting on individual customers. But the company said it is raising the bar for its ads to safeguard brands.
"[A]s announced, we've begun an extensive review of our advertising policies and have made a public commitment to put in place changes that give brands more control over where their ads appear," a Google spokesperson said in a statement to CNBC.
Google makes most of its money from advertisements and is one of the top online ad providers in the world. The problem of offensive content also plagues Google's competitors — especially when it comes to video, advertising professionals told CNBC.
— CNBC's Michelle Castillo contributed to this report