For decades, Walmart has attracted attention, and taken heat, for how it treats its work force, including paying low wages and creating unpredictable schedules.

Now, the giant retailer is teaming up with Silicon Valley to try to ease some of its workers’ financial strain.

This week, the nation’s largest private employer will begin providing its more than 1.4 million workers a service that will allow them to receive wages before their next payday.

Instead of waiting two weeks between paychecks, Walmart workers can now use an app to access a portion of wages for hours they have already worked. The goal is to help workers avoid costly payday loans and other debt traps.

“We believe this is the right thing to do, and we are happy to champion it,” Judith McKenna, Walmart’s chief operating officer, said in an interview.

But Walmart’s new digital initiative also highlights, albeit unwittingly, the financial struggles of Walmart’s low-wage work force. Even as the economy strengthens, many retail and service industry workers are not earning enough to make ends meet.

“It sounds like this may be a useful service but it doesn’t tackle the fundamental problem Walmart workers suffer,” said Paul Sonn, general counsel of the National Employment Law Project, an labor advocacy group. “Their paychecks are too small.”

The app, which is called Even, also helps workers manage their finances by pinpointing exactly how much they can safely spend before their next paycheck. Walmart pays a fee on behalf of the workers to the technology firm that runs the app.

The Even app has been used by other employers, but never on such a large scale as Walmart is using it. Ms. McKenna said employees who are less stressed about their financial stability “feel more confident and more settled at work.”

The minimum starting wage at Walmart is $9 an hour, which is $1.75 higher than the federal minimum wage but lower than the starting wage at retailers like Costco, which pays $13 an hour, and Target, which recently raised its entry-level wage to $11 an hour.

The average hourly wage for a full-time Walmart worker is $13.85, while the average hourly wage at Costco is about $24.50.

Every Walmart employee can use Even’s financial planning tool, and obtain eight payments, known as instapays, per year free of charge. For most of the workers, the instapays will be deducted from their next paycheck. The workers can pay extra if they want more than eight instapays.

Alexis Adderley, who works nights in a Walmart distribution center in Fort Pierce Fla., has started using the Even app as part of a pilot program.

At first she was suspicious, she said, that the app was yet another in a long line of financial products like payday advances and “overdraft protection” that end up driving low-income workers deeper into a hole.

But Ms. Adderley, the mother of four boys ages 8, 7, 4 and 2, said she had been pleasantly surprised.

The app, which connects to her bank account, calculates how much she pays for housing, food and phone bills and tracks when she makes big monthly payments. With that data, Even provides Ms. Adderley a real-time estimate of how much she can spend in a given day.

She earns $19.25 an hour, more than the average Walmart employee, and works 30 hours a week. But money is still tight, especially since she was forced to leave her home after Hurricane Irma. Earlier this week, the app warned Ms. Adderley, 30, that she had only enough money to safely spend $9.08 before her next paycheck.

“I would love to save more,” she said.

Walmart executives said they learned about Even after reading a New York Times article about the firm a few years ago. The retailer is also working with another tech firm, PayActiv, which facilitates some of the payments.

These partnerships reflects Walmart’s broader effort to make inroads in Silicon Valley, where the old-line retailer is seeking to acquire talent and ideas to boost its digital heft in its battle with Amazon.

Before creating Even, one of the firm’s co-founders, Jon Schlossberg, had developed an app called Knock, which allows phone users to unlock a phone by knocking on it.

Idealistic and flush with money from the success of Knock, Mr. Schlossberg said he began studying how a cash shortage affects people’s physical and mental well-being.

“It is a fundamental problem with the capitalistic society,” Mr. Schlossberg said in an interview.

Mr. Schlossberg, 30, said he set out to create a product that could reduce the stress associated with financial strain, joining a crowd of other so-called fintech start-ups seeking to disrupt the traditional banking model.

Landing a deal with such a large employer was a watershed moment for Even and PayActiv.

Walmart pays a small fee to Even to allow workers to withdraw their wages ahead of payday. Workers can take out only a portion of wages that they have already earned during the two-week pay cycle — so technically, Even says, these are not loans.

“You have earned this money,” said Safwan Shah, founder of PayActiv. “Who decides you should get paid every two weeks?”

Labor groups say the best investment Walmart could make is not in a new app, but in increasing wages.

“All of these solutions to help people live paycheck to paycheck puts the burden on the worker, not the employer,’’ said Carrie Gleason, who works on issues affecting retail and other low-wage workers at the Center for Popular Democracy, an advocacy group.

Walmart and the fintech firms say cash flow issues are not just a problem for the poor, but affect a broad segment of Americans.

Ms. McKenna said Walmart was making a “reasonably substantial investment” in paying for the Even service for its employees. The company raised starting wages nearly three years ago, and Ms. McKenna pointed out that Walmart has also increased employee training programs that aim to advance workers into management, where they can earn more.

“We continue to look at investing in our associates,” Ms. McKenna said.