Athletics: Paula back to her best in New York.
Radcliffe, who gave birth to daughter Isla in January, clocked two hours 23 minutes and nine seconds, holding off Wami by 23 seconds.
Two-time defending champion Jelena Prokopcuka finished third, clocking 2:26.13 - three minutes and four seconds behind Radcliffe.
The Briton picked up a winners' cheque for more than pounds 62,000, 26 months after signing off with a World Championships marathon title run in Helsinki.
Wami was considerably rewarded for her second place, however. In beating Prokopcuka she also picked up around pounds 240,000 as the first winner of the World Marathon Majors Series.
Radcliffe, 33, had led the entire race with Wami in her shadow, just 35 days after the Ethiopian had won the Berlin Marathon.
The Briton headed straight to the front on the mile-long climb to the crest of the Verrazano Bridge that took the race from Staten Island to Brooklyn.
Radcliffe said: "It was tough at the end, it was weird, my legs got tired and when she came alongside me I thought this was not happening to me again.
"I've had years and years of her outsprinting me on the track and I thought she's not going to do it in a marathon.
"I got a real shock when I crossed the line and looked behind because she was right alongside me at 400 metres to go."
Radcliffe's next big goal is the Beijing Olympics next year and she added: "It's always been the big target.
"This was about establishing myself to all the people who thought having a baby would be the end of my career, I never thought it would be.
"I have my qualifying time now and I can just carry on with the preparations."
Britain's Paula Radcliffe