Shares of sneaker maker Allbirds Inc. rose 64% in their market debut Wednesday, valuing the company at about $3.9 billion.

The San Francisco-based company, founded in 2015, makes a range of apparel but is best known for its low-profile shoes, which have gained popularity especially among tech-industry workers. One Silicon Valley employee told The Wall Street Journal last year that more than half his colleagues were wearing them.

Allbirds...

Shares of sneaker maker Allbirds Inc. rose 64% in their market debut Wednesday, valuing the company at about $3.9 billion.

The San Francisco-based company, founded in 2015, makes a range of apparel but is best known for its low-profile shoes, which have gained popularity especially among tech-industry workers. One Silicon Valley employee told The Wall Street Journal last year that more than half his colleagues were wearing them.

Allbirds was last trading at $24.59, a rise from the initial public offering price of $15.

Most of Allbirds’s sales come from the internet, with e-commerce representing about 89% of revenue last year, the company said in a regulatory filing. Distribution reaches 35 countries. It also has stores, including about a dozen in the U.S. and others in Europe and Asia for a total of 27 as of June 30.

The company hasn’t been profitable, but sales have risen as Allbirds markets the brand’s comfort and its use of sustainable materials.

In the first six months of 2021, revenue increased to $117.5 million, up from $92.8 million during the same stretch of 2020. But the company’s loss steepened, in part because administrative and marketing expenses were higher as well.

It posted a net loss of $21.5 million, compared with a loss of $9.3 million in the first half of 2020.

Allbirds has said it could benefit from pandemic trends that have blurred the bounds of traditional workday attire, because it says its shoes are comfortable but dressy enough for some business settings. On the other hand, changing consumer behavior raised challenges during the public-health crisis.

“Covid was more a headwind than a tailwind for us,” said Joey Zwillinger,

the company’s co-founder and co-chief executive. The lockdowns kept people home, and they weren’t buying as many shoes. As the world reopens, sales at Allbirds are “reaccelerating,” he said.

The company has also been growing its other apparel offerings. In August, it launched a line of athletic gear made from wool and from yarn created from tree pulp, an approach it said is more sustainable than workout clothes made from synthetic material.

Though Allbirds is a relatively young company at 6 years old, going public now felt right, Mr. Zwillinger said.

“This is definitely the big leagues,” he said.

Allbirds is one of a handful of companies reaching public markets this fall that emphasize sustainable business operations and charitable practices. The company says that it has sought to cut synthetic materials from its shoes, some of which are made of wool or use plant-based leather.

Warby Parker Inc., an eyeglasses company that went public in a recent direct listing, touts a “Buy a Pair, Give a Pair” program that donates products to people who don’t have access to eye care. Rent the Runway Inc., which went public last month, emphasizes how its business of renting out clothes instead of selling them reduces fashion’s environmental impact.

These socially driven approaches can appeal to consumers and to investors seeking to direct funds responsibly—especially given the rise of investment funds driven by environmental, social and governance principles.

But they can also add costs compared with the old-fashioned model of maximizing profit.

“Our focus on using sustainable materials and environmentally friendly manufacturing processes and supply chain practices may increase our cost of revenue and hinder our growth,” Allbirds said in a filing.

The stock is trading on the Nasdaq under ticker symbol BIRD.

—Corrie Driebusch contributed to this article.

Write to Matt Grossman at matt.grossman@wsj.com