Grimaldi, 27, sat in bronze position heading into the final round of the T47 long jump with her best jump of 5.75m.
But Denmark’s Bjoerk Noerremark, who sat in fourth and jumped before Grimaldi, pulled off an astonishing personal best of 5.76m to sneak ahead by 1cm into bronze position.
Grimaldi, whose personal best is 5.96m, fouled on her final jump to finish fourth in one of the toughest T47 long jump fields in recent years.
"I didn’t put my best foot forward today. I was really stressed ... I wasn’t able to settle down", Grimaldi told TVNZ last night.
"I think the first round foul really threw me, which it shouldn’t, I mean it’s what I do. I know how to fix that. I’m still really proud."
World record holder Kiara Rodriguez, of Ecuador, won gold with 6.05m to set a Paralympic record. She surpassed the previous mark of 5.76m set by Grimaldi in Tokyo.
Petra Luteran, of Hungary, won a surprise silver with a personal best of 5.85m and Noerremark won bronze.
It just was not to be for Grimaldi, who was the two-time defending champion after winning gold in Rio and Tokyo.
In a night that featured board and run-up issues for most athletes, Grimaldi took a little while to find her feet.
After a foul on her first attempt, Grimaldi breathed a sigh of relief when she jumped 5.65m on her next attempt to hold second.
Then Luteran came through with her personal best jump to overtake the New Zealander.
Grimaldi pulled out of her next jump, recording a mark of 4.03m, and bounced back with 5.75m and 5.74m in the next two rounds and eventually fouled her final attempt.
Earlier this week, Grimaldi claimed her first Paralympic track medal, winning bronze in the 100m to set an Oceania and national record of 12.20sec.
She rounds out her Paralympic campaign with the 200m, which starts with the heats tonight.
Robinson sixth in 'last ever' javelin competition
Dunedin thrower Holly Robinson was in action early this morning as she tried to defend her F46 javelin title, but came sixth, and says it was her last competition in that sport.
Robinson has a bronze medal to take home for the F46 shotput at this year's Games.
The 29-year-old started promisingly early this morning (NZ time), launching the spear out to a season’s best 39.03m with her opening effort - which was retaken after she successfully protested an incorrect measurement- to take a first round lead, Paralympics NZ said.
Unfortunately for the 29-year-old two-time former Paralympic medallist in this event (silver in Rio and gold at Tokyo), that was as good as it got as she struggled to nail the technical complexities of the event and what followed was five successive fouls in a high-class and dramatic battle for the medals.
Naibys Daniela Marillo Gil of Venezuela secured gold in round six with a stunning Paralympic record throw of 43.77m ahead of Uzbekistan's Shahinakhon Yigtalieva, who posted an area record of 43.12m. Rio 2016 champion Hollie Arnold picked up bronze with a best of 40.59m.
Robinson said she had mixed emotions after the result.
“I am really proud of how I attacked today’s performance in terms of my mindset and enjoying the competition, but I’m disappointed with the distance and not defending my title, so it is a mix of emotions for me.
"This will be my last ever javelin competition. I’ve done this for many years, but my body is ready to not be throwing javelin anymore.
"Reflecting on the last 12 years since London 2012 I am hugely proud of what I achieved.”
On today’s performance she said: “It was a timing and rhythm issue today. The last few years have been disruptive for me. My body is getting older I’ve had elbow surgery.
"I thought I might be lucky today and get one away, but I wasn’t lucky. That’s sport.
"It was a great competition one of the best in our class for a long time which was exciting. I can’t wait to see the future of this event.”
