Just as we thought we were ready to embrace rich, deep hair shades for autumn, Jessica Chastain has taken us in the opposite direction. The actress, 49, looks unrecognisable after trading her signature red locks for a gleaming blonde bob. With her bouncy, Hollywood curls, it seems she's taking notes from Marilyn Monroe's beauty playbook. Gentlemen prefer blondes, after all.

jessica chastain blonde bob transformation
Katie Flores
The new blonde shade makes an appearance on the red carpet

It appears the transformation has been on Jessica's beauty moodboard for a while. Last month, she was spotted at the US Open sporting a sweet strawberry blonde shade. The final transformation made its red-carpet debut last night at the Other Mommy premiere.

new york, new york september 12: jessica chastain in the stands on day fourteen of the 2026 us open at usta billie jean king national tennis center on saturday, september 12, 2026 in flushing, ny. (photo by shea kastriner/usta via getty images)
Shea Kastriner
It appears she started making the transition to blonde last month

‘It’s a real transformation,’ says Jason Collier, celebrity hairstylist and Key Opinion Leader at Jerome Russell Bblonde. ‘What makes it so striking is that it feels like a complete departure from the image we’re used to seeing.’

He explains, ‘Hair colour plays such a huge role in how we perceive someone, particularly when they’re known for one very distinctive shade. Jessica’s red hair has become part of her signature look, so moving to blonde instantly changes the overall impression.’

jessica chastain blonde bob transformation
getty images
Jessica before and after the blonde transformation

The fact that we had to do a double-take goes to show the power of a hair transformation. ‘Red tends to bring warmth, intensity and vibrancy to the face, whereas a lighter blonde can feel softer, brighter and more ethereal,’ says Jason. ‘The colour change makes her features stand out in a completely different way.’

Anyone who's ever considered going blonde will know that not all shades are created equal. ‘A well-chosen blonde can be incredibly flattering at any age, but as we get older, the right tone can help brighten the complexion and soften the overall look,’ says Jason.

jessica chastain blonde bob transformation
Emma McIntyre
A creamy blonde, like this, brightens the complexion

Jason tells us it’s all about choosing a tone that complements your natural colouring, and it seems Jessica has gotten the formula just right. ‘What I particularly like about this blonde is it’s creamy rather than icy. It has a soft, luminous quality that reflects the light beautifully without looking overly ashy or stark against the skin,’ says Jason.

The colour change is only one part of Jessica's transformation. While her usual sleek, smoothed-down style is undoubtedly polished, the rounded, Monroe-inspired curls are the height of glamour, and cleverly creates the illusion of thicker locks.

jessica chastain blonde bob transformation
Michael Buckner
The Old Hollywood styling looks phenomenal on Jessica

‘The beauty of Old Hollywood styling is that it’s all about shape, volume and movement,’ Jason explains. ‘The softly sculpted waves create a rounded silhouette that adds fullness. Those curves give the style body and structure without needing lots of layers.’

Being a red-carpet affair, Jessica brought her beauty A-game. But Jason says the look is surprisingly wearable (and easier to recreate than you might think). So, for those also wanting to channel their inner Monroe, Jason tells us exactly how.

‘You’ll want to tart by applying a volumising mousse, like Bstyled Thickening Mousse to damp hair, focusing on the roots for lift and through the lengths for hold. Blow-dry using a medium round brush, directing the front section away from the face to create that sweeping shape,’ he says.

Jerome Russell BStyled Thickening Hair Mousse

BStyled Thickening Hair Mousse

Jerome Russell BStyled Thickening Hair Mousse

Credit: amazon

For the curls, he recommends a medium barrel-curling tong, curling sections in the same direction for a polished look. For the vintage effect, he says to let the curls cool before brushing through. ‘The trick is to not leave the curls too defined; that’s what gives you that soft, expensive-looking Old Hollywood finish.’

jessica chastain blonde bob transformation
Emma McIntyre
Try brushing through curls for that vintage feel

As a final touch, he recommends finishing with a light-hold hairspray for hold, and a touch of the Bstyled Hair Oil for that glossy, red-carpet worthy finish.

Jerome Russell BStyled Hair Serum

BStyled Hair Serum

Jerome Russell BStyled Hair Serum

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Credit: amazon

We're certainly taking notes. Jessica's transformation has us seriously considering a trip to the salon.