Green Living

The Best Sustainable Formal Dresses & Wedding Guest Dresses for Every Occasion

Published

1 day ago

November 13, 2026

Alice Rush

Whether you’re planning to be a guest at a wedding, or attend a prom, gala, or any other special occasion, these ethical and sustainable formal dresses will be just the fit.

A lot of formalwear is made from irresponsibly sourced silk or polyester and is worn just once. It’s time to turn that around!

This guide will share sustainable formal dress options that have frocks you can rock to weddings, dances, galas, concerts, or any other event you have coming up.

How to Find Sustainable Formal Dresses

The most sustainable garment is the one already in your closet!

Do you have a special occasion dress or piece of formalwear that could fit the bill? While wearing an outfit only once to an event has unfortunately become the norm with social media, we can help counteract the culture by normalizing outfit repeating to special occasions again!

Another sustainable option is to make the most of what already exists by borrowing from a friend or family member or swapping with someone you know has a formal dress. This is something my friends and I did for high school dances like homecoming and prom. A friend’s Junior Prom dress became my Senior Prom dress the next year!

If there’s no one with your style and size, you can also expand your search of formalwear by browsing online resale platforms. Vestiaire Collective has a fabulous selection of dresses from designer brands for great prices, as does The RealReal. I’ve used The RealReal site to purchase dresses for weddings and other occasions.

If you just need a special occasion dress for one event, consider rental sites like Rent the Runway that offer affordable ways to get formalwear for a limited time.

If none of these options are available to you or you really feel ready to invest in an extra-special garment that you can wear for years to come, keep scrolling for our list of brands with sustainable and ethical formal dresses.

Brands With Sustainable Formalwear & Special Occasion Dresses

These brands have party-perfect minis, chic cocktail dresses, elegant evening gowns, and even pieces that would make for fabulous sustainable prom dresses! (You might also want to check out this guide for sustainable wedding dresses or this guide for more causal eco-friendly dresses.)

Price Key:

$ = Under $120
$$ = Under $250
$$$ = Under $400
$$$$ = $400+

Note that this guide contains partners and affiliate links. As always, all brands meet rigorous standards for sustainability and are brands we truly love — and that we think you’ll love too!

1. The RealReal

Best for: secondhand designer gowns and cocktail dresses

Whenever I’m looking for a wedding guest outfit or dress for another special occasion, The RealReal is my first stop. From gowns to cocktail attire, mini to maxi dresses, designer to contemporary, The RealReal is a mecca for dresses that sparkle and shine — at up to 70% off original prices.

Though you should expect an equally wide array of prices, from steals at under $70 to vintage designer looks coming in at $10K+. Be sure to use the price filter to find something that suits your budget.

Conscious Qualities: Secondhand

Size Range: XXS – 5XL
Price Range: $ – $$$$

Shop The RealReal

Blue formal dress, silver sparkly formal dress, and green cocktail dress from secondhand designer platform The RealReal

2. Ninety Percent

Best for: affordable special occasion dresses

A responsibly-made occasion dress doesn’t have to break the bank. UK-based Ninety Percent has dresses made from lower impact materials like MicroModal and better practices like solar-powered production coming in at just around $100.

Most pieces are made at EchoTex, a facility in Bangladesh owned by the brand’s co-founder for maximum transparency. Best yet, 90% of the brand’s profits are shared across five causes and the workers behind the brand.

Conscious Qualities: Traceable Production, Profit Sharing

Size Range: UK 4-18 (US 0-14)
Price Range: $

Shop Ninety Percent

3. Reformation

Best for: going-out and wedding guest dresses

Reformation is a leader on sustainability among larger fashion brands, between their climate positive roadmap and better material sourcing (including recycled cotton, TENCEL Lyocell, and regenerative fabrics) to their supply chain transparency, limited production model, and circularity practices.

And the brand is making it easy to shop for sustainable special occasion dresses with their selection features like “Going Out Dresses” and “Wedding Guest Dresses”.

Conscious Qualities: Lower Impact Materials, Responsible Production Practices, Decarbonization Initiatives

Size Range: 0 – 12
Price Range: $$ – $$$

Shop Reformation

4. OMNES

Best for: made-to-order upcycled evening wear

Making each piece to order using upcycled materials, Bastet Noir is a zero-waste fashion label. The brand’s sustainable formal dresses and other elegant apparel — including silk jumpsuits — are made by women in North Macedonia. 100% of Bastet Noir’s profits are reinvested into the women’s businesses and their children’s education.

Conscious Qualities: Repurposed Materials, Made-to-Order, Gives Back

Size Range: 4-10 + custom sizes
Price Range: $

Shop Bastet Noir

5. AMUR

Best for: formal dresses for black tie dress codes

Standing for A Mindful Use of Resources, AMUR uses natural materials like cotton and recycled fibers like recycled polyester.

AMUR is the brand on this list with true gowns, so if you’re looking for a more sustainable prom dress or black tie occasion outfit, AMUR would be our pick. That said, the brand doesn’t have as much transparency on labor practices as the others in this guide.

Conscious Qualities: Natural & Recycled Fabrics

Size Range: XXS-XL
Price Range: $$$$

Shop AMUR @ Revolve

6. SeamsFriendly

Best for: natural fiber special occasion dresses

Can you find natural fiber formal or wedding guest dresses? SeamsFriendly is proving that the answer is yes. Crafted from 100% cotton or 100% linen in classic A-line and fit-and-flare dress fits, these are the perfect dresses for summer showers and weddings.

And since each piece is made-to-order just for you, you can select a fabric of your choice, select custom sizing at no additional fee, and customize the piece in dozens of other ways such as sleeve length, neck line, and even adding nursing-friendly zippers at the bust.

Conscious Qualities: Natural Fibers, Made-to-Order

Size Range: Custom sizing
Price Range: $

Shop SeamsFriendly

7. Christy Dawn

Best for: Semi-formal dresses for showers, baptisms, and casual weddings

Christy Dawn’s dresses are vintage-inspired but totally timeless. Their feminine frocks can be worn as house dresses or semi-formal wear to weddings, bridal showers, baptisms, or other not-quite black-tie occasions. Their dresses are either made from reclaimed fabrics ethically in Los Angeles or from regenerative organic cotton that is sourced in partnership with a small collective in India.

You’ll also find sustainable special occasion dresses from Christy Dawn made with regenerative silk, like the dress pictured here!

Conscious Qualities: Reclaimed or Regenerative Fabrics, Ethical Production

Size Range: XS-3XL (extended sizing collection)
Price Range: $$$

Shop Christy Dawn

8. BAACAL

Best for: mid-size and plus-size slip dresses

Frustrated that brands often stop their size range at 12 despite the average American woman wearing size 16, BAACAL creates conscious clothing for the “true majority”: women who wear sizes 10-22. The plus-size sustainable fashion brand uses upcycled, vintage, and other existing materials for their collections.

Conscious Qualities: Upcycled Fabrics, Small-Batch Collections, Size-Inclusive

Size Range: Unique sizing system of 1-4 (equivalent to 10-22)
Price Range: $$$

Shop BAACAL

9. Lahive

Best for: bold special occasion outfits

Bold and unique, Lahive’s stand-out dresses and other ethical formal wear will make a statement at cocktail hour or a night out downtown. The LA-based brand produces their luxe, textural pieces in small batches using upcycled materials in a factory run by solar power.

And this unique brand is sold at WOC-owned marketplace, ourCommonPlace.

Conscious Qualities: Upcycled Fabrics, Renewable Energy, Local Production

Size Range: XS-XL
Price Range: $$$

Shop Lahive

You Might Be Asking…

Are there affordable sustainable formal dresses?

Thankfully the answer here is yes! Ninety Percent has occasion dresses at around $100 or under, and SeamsFriendly’s made-to-order dresses run about $70 to $80. The RealReal is the other budget route, with plenty of formal dresses under $100, though prices can also run quite high for designer items so the price filter is your friend.

What’s a sustainable option for a wedding guest dress?

Reformation has a dedicated Wedding Guest Dresses category to make it easy. SeamsFriendly makes wedding guest dresses in 100% cotton or linen that could work for casual summer weddings, and Christy Dawn works for casual or semi-formal weddings. For a black-tie wedding, I’d look at AMUR or OMNES’ gowns.

Where can I find sustainable formal dresses in extended or custom sizes?

SeamsFriendly is made to measure, with a bust range of 26 to 72 inches and petite, regular, and tall heights. Christy Dawn has an extended collection up to 3XL, and The RealReal runs XXS to 5XL.

What’s the most sustainable way to get a formal dress for one event?

Wear or borrow what already exists first, then shop secondhand, either at your local consignment shop, thrift store or an online platform like The RealReal or Vestiaire Collective. Renting from a service like Rent the Runway or ByRotation can make sense for a single event you won’t repeat, but rental fees can be quite high so I find that buying secondhand is usually a better bang for my buck if I can wear it more than once. If none of those options make sense for you, then this guide has plenty of sustainably-minded brands to select from.

Are there sustainable prom or black tie gowns?

AMUR is the one brand in this guide that has true gowns, though OMNES and Reformation have some pretty elevated evening options too. The RealReal is my pick for a secondhand option.

What fabrics are best for sustainable special occasion or formal dresses?

This one is a bit tricky because natural fibers like linen don’t always give off the most elevated “evening wear” feel. That said, I’d still suggest a high-quality structured cotton or linen for a more casual affair. If you’re going more formal and want something more fluid, sheer, plush, or dramatic (like chiffon, organza, or tulle) then we likely have to extend our fiber options. The exception potentially being velvet or lace which can be — but often aren’t — made with cotton.

Instead we might look for peace silk, silk alternatives like TENCEL Lyocell (made from wood pulp), or recycled materials like recycled silk or recycled polyester. Recycled polyester isn’t my favorite sustainable fiber choice, but to achieve certain a satin glossy appearance without the price tag of silk, it is often the fiber of choice. Since you’d be washing an evening dress less often, though, the microplastic impact is likely less than an everyday piece like a polyester sweatshirt, though.