The de Blasio administration announced on Friday it had hired a former spokesman for Bernie Sanders to run its day-to-day media strategy.

The former spokesman, Mike Casca, 27, will become Mayor Bill de Blasio’s communications director, helping to shape the approach of a media operation that has gone through several rounds of reshuffling and has been at odds with reporters over its decision to scale back traditional mayoral news conferences to one a week.

His predecessor in the position, Andrea Hagelgans, will become a senior adviser to the mayor focused on communications, and one of the highest-ranking women in City Hall. Advisers to Mr. de Blasio have credited Ms. Hagelgans, 38, with pushing a focus on television and social media as well as creating in-person events for the mayor aimed at drawing maximum media attention.

“We know that visuals help people understand what we’re trying to communicate,” she said in an interview. “But that doesn’t mean we’re not talking to print reporters.”