J.Crew Group Inc. said it hired former Victoria’s Secret executive Jan Singer as its next chief executive, as it seeks to revitalize its namesake brand and reverse a long sales slump.

Ms. Singer will join the closely held company’s board and assume oversight of the J.Crew and J.Crew Factory brands, starting Feb. 2, the company said Tuesday. Her appointment ends a more than yearlong search for a permanent CEO.

The...