By Jeff Horwitz

Former top Facebook Inc. deputy Chris Cox is returning to the social-media giant, just over a year after leaving amid disagreements with CEO Mark Zuckerberg over the company's direction.

Mr. Cox, who was one of Facebook's earliest engineers, announced his plans to return as the company's head of product, the job he resigned in March 2019. The core of the role is executing Mr. Zuckerberg's vision for Facebook's platforms, and Mr. Cox was known to have disagreed with the CEO's plans to move toward unifying the company's products around encrypted messaging.

In a Facebook post announcing the move, Mr. Cox said discussions about his return began about a month ago when he reached out to Mr. Zuckerberg. After spending a year spending time with his family, working to support Democrats in the 2020 elections and playing with his reggae band, Mr. Cox said, he felt called to return.

"2020 refocused us all, on a public health crisis, an economic crisis, and now a reckoning of racial injustice. The world is unsettled, divided. People are struggling when things were already hard," he wrote, calling Facebook "the best place for me to roll up my sleeves and dig in to help."

Mr. Cox said he had continued to follow Facebook closely and was "encouraged by progress on so many of the big issues facing us."

Write to Jeff Horwitz at Jeff.Horwitz@wsj.com