Idowu won the world triple jump title last year in Berlin last August
Phillips Idowu leapt to a world-leading 17.48 metres to win the triple jump at the Grande Premio Brasil Caixa de Atletismo meeting in Rio de Janeiro.
The Briton's mark was 1cm further than that posted by Cuba's Alexis Copello at the first Diamond League meeting in Doha earlier this month.
Copello was second in Brazil behind world champion Idowu with 17.31m.
Britain's Dwain Chambers also looked impressive in clocking 10.11 seconds to finish second in his 100m race.
American Mike Rodgers, whom Chambers beat to win 60m gold at the World Indoor Championships in March, took victory in 10.06.
But Chambers finished ahead of a decent field including Trinidad & Tobago's Olympic silver medallist Richard Thompson, Jamaica's Lerone Clarke and Antigua's Daniel Bailey.
At the Loughborough International meeting, Jessica Ennis warmed up for a possible assault on Denise Lewis's British heptathlon record next weekend.
The world champion won the high jump with a clearance of 1.93m, the highest she has gone since 2007 and just 2cm off her personal best.
She earlier won the 100m hurdles, perhaps her strongest discipline, in a wind-assisted 12.85secs and finished the day by throwing 43.83m in the javelin.
Ennis, 24, takes part in the multi-event meeting in Gotzis, Austria, next weekend and Lewis's 10-year-old record could be under threat.
Her current best score for the heptathlon is 6,731 points, which she set in winning World Championship gold in Berlin last summer, while Lewis' mark is 6,831.
"I feel really good, everything is going to plan and I'm feeling a lot stronger and quicker," she said after the hurdles.
"I just feel in really good shape. I definitely think I'm quicker than last year."