ozens in what authorities described as terrorist attacks.
The Dow Jones Industrial Average rose 15 points, or 0.1%, to 17639 after falling early in the session. The S&P 500 gained 0.2%, while the Nasdaq Composite added 0.4%.
The Stoxx Europe 600 fell more than 1.3% before paring losses to 0.2%.
In recent years, financial markets have reacted swiftly to attacks in Western cities before quickly recovering. Markets from equities to bonds and gold were little disrupted by the killing of at least 129 people in Paris last November.
The market "has largely grown numb to them and shrugged them off," said Keith Bliss, senior vice president at brokerage Cuttone & Co. "Unless we see another attack on the heels of this or another attack in a major metropolitan center...I don't think the market's going to react."
Travel and leisure stocks, however, fell after the explosions hit Brussels' international airport and a subway station near European Union institutions. Belgian officials shut down the entire public transport network in Brussels and raised the terror alert across the country to its maximum level.
In the U.S., Delta Air Lines shares fell 0.9%, while American Airlines Group dropped 1.2%. Cruise operator Royal Caribbean Cruises lost 3%, while competitor Carnival fell 2.3%. In Europe, shares in Air France-KLM fell 4%, and Thomas Cook Group dropped 4.3%.
"It's hard to say what the long-term impact is, but it's not good," said Sanjiv Shah, chief investment officer at Sun Global Investments. "There are worries about security, the impact on growth, greater restrictions on travel."
Investors appeared to take heart in the market's largely muted reaction to the attacks, particularly because it occurred amid relatively low trading volumes, which tend to exacerbate market moves, said Peter Costa, president of trading firm Empire Executions.
Trading volumes have been light in recent sessions. On Monday, fewer shares traded hands than any other day this year. The holiday-shortened week is also contributing to light trading, said Mr. Costa. The U.S. stock market will closed for Good Friday.
Stocks have steadily climbed from steep losses at the beginning of the year, spurred by improvements in U.S. economic data, a rebound in commodities prices and a more dovish stance from the Federal Reserve and European Central Bank.
As volatility recedes, investors are now assessing whether the rally has further to go.
"Central banks have created a bit of a buffer for markets, but we think there are still sufficient uncertainties that will keep markets volatile this year," said Eric Wiegand, senior portfolio manager at U.S. Bank Wealth Management, pointing to questions around China's economy, commodity prices and the U.S. labor market going forward.
In commodities, gold rose 0.4% to $1,248.20 an ounce, while U.S. crude oil fell to $41.45 a barrel in a choppy session.
The yields on 10-year German and U.S. government bonds fell slightly as prices rose.
In economic news, a reading of the U.S. manufacturing sector this month rose slightly from February.
The composite purchasing managers index for the eurozone rose in March, beating investors' expectations, while German business sentiment brightened as companies grew more upbeat about the country's outlook.
Despite the recent pickup in data, "We're experiencing a slow growth world, and I can't see that changing," said Gary Greenberg, head of emerging markets at Hermes Investment Management.
The Shanghai Composite Index snapped a seven-session winning streak, falling 0.6% after Chinese authorities tempered a pledge to accelerate the development of China's capital markets and guided the yuan weaker.
Japan's Nikkei Stock Average ended 1.9% higher as it reopened from a holiday.