SHANGHAI—China emerged from the weekend Group of 20 meeting with a new measure of trust from major trading partners that it won’t significantly devalue the yuan. Persuading investors might be tougher.

Chinese Premier Li Keqiang and central bank chief Zhou Xiaochuan worked hard to dispel worries among visiting G-20 finance ministers and central bankers that their economic strategy hinges on weakening the yuan’s exchange rate.

The message was “heard loud and clear” that Beijing has “no intent, no determination, no decision whatsoever to devalue the yuan,” said Christine Lagarde, the managing director of the International Monetary Fund, after the weekend meetings in Shanghai.

Global anxiety had grown in recent weeks that China would engineer a significant yuan devaluation as it endures the slowest economic growth in a quarter-century.

Right before the formal talks began, Mr. Zhou spoke forcefully in English. “There is no basis for persistent [yuan] depreciation from the perspective of economic fundamentals,” he told a forum of investors. Then, the premier addressed structural-reform plans during a video conference with the G-20 on Saturday.

The comments earned praise from U.S. Treasury Secretary Jacob Lew. “There was a real need for that communication because private conversations weren’t penetrating the consciousness of the many observers who wanted to know what China was trying to accomplish,” he said.

On Sunday, Mr. Lew made a point that such candor shouldn’t be a one-time event, saying in a meeting with Vice Premier Wang Yang in Beijing that it is critical that China’s exchange-rate policy be transparent and that Beijing “clearly communicate its actions to the market.”

The G-20 cited volatile capital flows, plunging commodity prices and the U.K.’s potential exit from the European Union as threats that could pitch the world into recession; it didn’t explicitly mention China. The financial chiefs vowed to speed up economic overhauls and to “use all policy tools—monetary, fiscal and structural” to strengthen growth, boost investment and ensure stability in financial markets.

Global markets have shuddered in recent months amid a souring outlook for world growth, overall weak demand, and worries that China’s economy may be slowing faster than Beijing acknowledges. The IMF warned last week it is likely to further downgrade its forecast in coming months.

“There’s clearly a sense of renewed urgency,” Ms. Lagarde said after the meeting.

Although the G-20 said countries may need to explore increasing spending, its promises fell short of calls by the IMF and others for a coordinated stimulus package to revive flagging output. And there was no discussion of the sort of currency accord suggested by some investors as a way to temper global economic turmoil, as officials insisted there was no major currency misalignment.

The G-20’s statement reflected a gathering consensus that many countries are depending too heavily on monetary policy to stimulate growth. The statement reiterated a pledge for countries to refrain from weakening their currencies to gain a competitive edge—a sign that concern remains about China, among others.

Beijing helped reduce anxiety at the G-20 with its rare effort to respond to international concerns by offering insight into authorities’ thinking, officials said. But investors have reason to remain cautious.

Chinese officials stopped short of pledging the yuan won’t lose value, only that they aren’t pursuing policies aimed at a devaluation. A continued erosion of China’s exchange reserves at the recent rate of around $100 billion a month could alter Beijing’s calculus and prompt it to blunt speculative yuan selling with a one-off devaluation. Chinese officials cite the country’s $3 trillion-plus pile of foreign currency as a huge source of stability.

While international policy makers said they were heartened by Beijing’s communication efforts, none suggested they learned anything new about how Chinese authorities would avoid a crisis or currency debacle as they wrestle with myriad economic challenges.

“They were precise enough,” said Pierre Moscovici, Europe’s economic commissioner.

Beijing’s recent communication effort, including a rare news conference by Mr. Zhou on Friday, encouraged some analysts. Yet, some say regular briefings from the central bank might be needed to encourage foreign investment into yuan-denominated assets, such as bonds.

Still murky after the G-20 is how Chinese authorities are actually managing the yuan.

Officially, the central bank attaches the yuan’s value to as many as three baskets of currencies of its trading partners—though Mr. Zhou told reporters Friday that among those, the dollar remains the most important, indicating the central bank continues to seek flexibility.

The basket model itself is a risk because it lacks transparency, and appears to provide opportunities for Beijing to cast blame elsewhere if the yuan falls, said David Loevinger, the U.S.’s former Treasury representative in China and now a fund manager at TCW in Los Angeles. Since the baskets include the euro and the yen, as well as the dollar, Mr. Loevinger said, China may now be trying to insulate itself from blame for any future currency turmoil by signaling, “Europe and Japan, you depreciate, we’ll depreciate.”

The reserves erosion may ultimately trump other concerns. If they continue to slip away, said Arthur Kroeber, managing director of Beijing research firm Gavekal Dragonomics, the question becomes, “frankly, how do you get out of this?”