Republican Federal Communications Commission commissioner Meredith Attwell Baker is planning to leave the agency for a job at Comcast Corp., according to people with knowledge of the matter.

Ms. Baker is expected to announce her departure as soon as this week for an unknown position at the Philadelphia-based cable giant. Comcast declined to comment, a company spokeswoman said.

Ms. Baker did not respond to several emails and phone calls for comment.

She came to the FCC in 2009 from the Commerce Department, where she was the acting head of the National Telecommunications and Information Administration, which oversees federal airwaves. At the agency, she oversaw a government coupon program that made it cheaper for Americans make the switch to digital-only television.