When the 2,073-foot Shanghai Tower topped out last month, it became China’s tallest building, and the second-tallest in the world (after Dubai’s Burj Khalifa) — a monumental achievement. But to Gensler, the firm that designed it, the $1.9 billion tower represents something more: It is the most complex project in the company’s 48-year history, an iconic foothold in a fast-growing Asian market, and the culmination of a two-decade-long relationship that has landed Gensler’s three executives in a uniquely collaborative C-suite. That’s a word you hear all the time from the trio: “collaboration.” They come from different backgrounds, each of which touches the different aspects of their business.
Andy Cohen, the self-described “old company man” of the bunch, studied design at Pratt and joined Gensler not long after. The firm works on everything from wine labels to chairs (it started out specializing in reimagining office spaces) to an entire city in Saudi Arabia. The variety of the work is reflected in the corporate structure: “Most firms are arranged around one star,” Cohen says. “In our case, it’s a constellation.”
Diane Hoskins arrived at Gensler in 1994 with an architecture degree and an MBA, as well as a background in real estate development. David Gensler, whose father, Arthur, founded the firm in 1965, is more “pure business,” he says, and worked at Morgan Stanley and a health care startup before joining. Still, every two years the three swap roles, overseeing different aspects of the company, from scouting and retaining talent to client relations to strategic planning and research. “The cross-pollination of expertise really is what spurs innovation here,” Hoskins says.
There is a more practical element to their partnership: They can have a CEO on (nearly) every continent, crucial for an $800 million company with 3,900 employees spread across 44 offices in 15 countries, 6,700 ongoing projects, and a client list that includes about half of the Fortune 100. David Gensler estimates he’s on the road 200 days a year, so his video meetings every Friday with his co-CEOs are “sacred.” He adds: “The thing that works is we’ve been around each other so long, we really have an affection for one another.”
Andy Cohen on their relationship: “We’ve been working together for 20 years. We can almost complete each other’s sentences.”
Diane Hoskins on diversity: “Innovation requires different points of view, so with the three of us, that permeates.”
David Gensler on philosophy: “We tackle problems from inside out, so what happens inside the building before the outside.”
This story is from the September 2, 2013 issue of Fortune.