A service was held outside the war memorial in Bridge Street to mark the occasion.
Flags were raised and a wreath laid by branch chairman Graham Casey.
Long service presentations were also held for Margaret and Jerry Wilson who are retiring after 25 years of standard bearing.
Branch secretary Tony Francis said: “I would like to thank all who attended in support, including the Peterborough Sea Cadets from TS Guildenburgh who turned out to help build the bridge between generations - they did their unit very proud.
“On a whole it was a memorable small service to mark the occasion, especially during these trying times, and everyone did me proud and I am thankful for their attendance and support.”
13. 100 year celebration for the Peterborough Royal British Legion
The service at the war memorial Photo: Midlands
14. 100 year celebration for the Peterborough Royal British Legion
The service at the war memorial Photo: Midlands
15. 100 year celebration for the Peterborough Royal British Legion
Long service presentations to Jerry Wilson who is retiring from standard bearing after 25 years with the branch by Vice Lord Lieutenant of Cambs Benjamyn Damazer EMN-210627-170549009 Photo: Midlands
16. 100 year celebration for the Peterborough Royal British Legion
Long service presentations to Margaret Wilson who is retiring from standard bearing after 25 years with the branch by Vice Lord Lieutenant of Cambs Benjamyn Damazer EMN-210627-170538009 Photo: Midlands