It's a Mystery, Charlie Brown
- Blwyddyn: 1974
- Gwlad: United States of America
- Genre: Animation, Comedy
- Stiwdio: Lee Mendelson Film Productions, Bill Melendez Productions
- Allweddair: detective, dog, beagle
- Cyfarwyddwr: Phil Roman
- Cast: Todd Barbee, Melanie Kohn, Stephen Shea, Donna Le Tourneau, Jimmy Ahrens, Lynn Mortensen