In a nail-biting close final, Valerie led after throwing a massive 20.42m on her second attempt.
Her effort put her streets ahead of her competitors, until Carter stepped up and threw her unbeatable 20.63m.
Valerie had a chance to take back the lead but her final throw saw a landing of 20.39m.
Already a double Olympic champion, Valerie had set her sights on becoming the first woman to win three gold medals for her sport.
So far, no New Zealand athlete has claimed three consecutive Olympic gold medals.
After the final, Valerie told Sky Sports she was not too disappointed.
“I am ok – it would have been nice to win, that was the whole goal, but that’s sport,” she told Sky Sports.
"I came out here and left my heart out here and I fought to the very end and after where I was last year to now, I've done a lot of work to be here today and I'm very blessed to be here today.
"It is my third Olympic medal and I've got to take it and run."
- WeddingsDying bride's perfect day: My final dream has come true
Woman's DayToday 2:25pm
- RoyalsPrince Harry's trick to beating a heatwave? ‘Budgie smugglers’, he says
Now To LoveToday 1:00pm
- TVWhat drove these celebs to sign up for Celebrity Treasure Island
Woman's DayToday 12:35pm
- Pregnancy & BirthWhy model Ashley Graham's baby bump photo has got everyone talking
Now To LoveToday 12:07pm
- RoyalsDuchess Catherine honours this lucky nine-year-old to celebrate World Photography Day
Now To LoveToday 11:15am
- CareerI loved him like a son: Phil Kingsley Jones remembers Jonah Lomu in his final years
New Zealand Woman's WeeklyToday 9:29am
- TVMatty McLean says he's lived some of his proudest moments on Celebrity Treasure Island
New Zealand Woman's WeeklyToday 9:09am
- TVThe redemption of former All Black Zac Guildford on Celebrity Treasure Island
Now To LoveYesterday 8:45pm
- TVKarl Burnett quits Celebrity Treasure Island as mental health suffers
Now To LoveYesterday 8:30pm
- Married at First SightMAFS' Cyrell Paule is expecting a baby with Love Island's Eden Dally
Now To LoveYesterday 1:21pm
- Pregnancy & BirthAll the gorgeous details from Samantha Hayes’ 'beautiful' baby shower
Now To LoveYesterday 12:17pm
- TVFour curious things we've learned about the stars on Celebrity Treasure Island
Now To LoveYesterday 10:42am
- TVThe first trailer for Married at First Sight NZ has been released and it's utter chaos
Now To LoveYesterday 9:48am
- RoyalsDuchess Meghan and Prince Harry jet off on another family holiday to the south of France
Now To LoveYesterday 9:15am
- FamilyWhy Karl Burnett is hoping to be voted off Celebrity Treasure Island
Woman's DayYesterday 8:30am