Families and colleagues of officers killed in the line of duty took part in the 10th annual service at St David's Hall in Cardiff in Wales.
Among those remembered was Metropolitan Police officer Pc Andrew Duncan, 47, who was killed in a suspected hit-and-run collision last week.
Greater Manchester Police officers Nicola Hughes and Fiona Bone - originally from Scotland - were honoured. They were murdered in a gun and grenade attack last September.
Sgt Joe Holness, founder of the National Police Memorial Day, said about 4000 police officers had died in the line of duty since modern policing records began in 1792. "There are between 10 and 15 fallen officers every year," he said.