Ireland's Sinead Delahunty, who won last year's race, was fourth but Diane Modahl could only finish a disappointing 11th.
Radcliffe, who won easily, learned the night before that Russia's Svetlana Masterkova, the 1996 Olympic gold medallist at both 800 and 1500 metres, had pulled out because of nausea and flu-like symptoms.
"Without the Olympic champion it certainly made life easier, though perhaps less challenging," said Radcliffe, who took command of the race shortly after the pace-setter, Jacqueline Martin of Spain, dropped out at the half-mile mark.
"Nobody was pushing, so I told myself I wasn't going to run along and wait for the others to move."
The 22-year-old from Loughborough, who won the junior division of the World Cross-Country Championships in Boston in 1992, had run mostly 5,000m races over the past few years. "For that reason, I was worried about my speed at the end, but it wasn't until the final steps that I could hear anyone behind me."
Isaac Viciosa of Spain took the men's race, with Ireland's Marcus O'Sullivan sixth and Matthew Yates of Britain eighth.
Steve Scott dominated the masters division - winning by nearly 20 seconds - and then outkicked Ireland's world indoor mile record-holder Eamonn Coghlan in a two-man Champions of the Mile race.
n Spain's European 10,000m champion, Abel Anton, won the Berlin marathon in a time of 2hr 09min 16sec. He finished 16 seconds ahead of Francis Naaly of Tanzania with last year's winner Sammy Lelei of Kenya, third. The women's race was won by South Africa's Colleen de Reuck in 2:26:35 from Poland's three-times winner Renata Kokowska and Marleen Renders of Belgium.