get on someone’s case

get on (one's) case

To start bothering someone about something. Oh, don't worry—I'll get on Pat's case until he agrees to go to the interview. It's too good an opportunity to pass up.See also: case, get, on

get on someone’s case

in. to start harassing someone about a personal problem; to annoy someone. (Compare this with get off someone’s case.) I’ll get on Tom’s case about being late so much. See also: case, get, on