Sean Atkins, who took over as president of MTV just a year ago, is leaving the TV network, becoming the latest Viacom Inc. executive to head for the exits in recent months.

Mr. Atkins will be succeeded by Chris McCarthy, who currently leads VH1 and Logo. Mr. McCarthy will add MTV to his responsibilities and continue to report to Doug Herzog, president of Viacom Music and Entertainment Group.

In a note to staff on Monday, Mr. Atkins said he would stay through January in an advisory role during the transition, calling his stint at MTV an “enriching and rewarding experience.”

At its “upfront” presentation to marketers this spring, Mr. Atkins trumpeted the network’s charge back into music programming. At the event, which happened to be held on the day of music icon Prince’s death, Mr. Atkins pledged to “put the ‘M’ back in MTV.” The network has been on the hunt for new media and creative agencies to help MTV regain its status as a hub for young people when it comes to music and pop culture.

Chris McCarthy has been named president of MTV, VH1 and Logo. Photo: Viacom

Still, the network, which has been particularly hard hit by young consumers’ shift to newer platforms, has struggled in the traditional linear TV ratings.

“The power of the MTV brand is its ability to let go everything it knows and reinvent for the next generation of youth, and I’m excited to push the boundaries of what it can be in this transformative time,” Mr. McCarthy said in a statement.

Under Mr. Atkins, who previously was the general manager and executive vice president of digital media and strategy at Discovery Communications, MTV also pushed into new digital terrain with its channel on Snapchat Discover, the app’s media destination. He revamped MTV News and rebranded VH1 Classic as MTV Classic, which features 1990s and 2000s MTV programming.

The departure comes at a tumultuous time for parent company Viacom, which spent much of this year entrenched in a boardroom drama with its controlling shareholder that ended with the ouster of CEO Philippe Dauman. Last month, Mr. Dauman’s interim replacement Tom Dooleyannounced his plans to step down in mid-November, and Viacom’s former sales chief Jeff Lucas also recently departed for Snap Inc.

Meanwhile, Viacom’s controlling shareholder has urged the company and CBS Corp. , which it also controls, to examine a possible merger.

Write to Steven Perlberg at steven.perlberg@wsj.com