The annual event took place Saturday afternoon into Saturday night at the Michael S. Cohen School in Bangor.
The event raises money for the American Cancer Society. Organizers said the American Cancer Society gives back to Maine cancer patients more per dollar than any other cancer organization in Maine.
At the relay, participants walk around the track in remembrance of those they've lost to the disease and for those still fighting.
"It's an amazing event where we can all get together and you can really build a new family here at relay too, one who really understands the cancer process and how difficult it can be," said Jessica Sargent, a relay organizer.
This year's relay featured food trucks and a bounce house.
Relay for Life of Penobscot raises funds all year long.