Four in 10 millennials are overwhelmed by debt, with almost half spending at least 50 percent of their monthly paycheck paying off debt, a new study by Wells Fargo found. More than half—56 percent—reported living paycheck to paycheck.
Credit cards are the biggest drain on millennials' wallets, followed by mortgages and student loans.
However, millennials are optimistic—72 percent said they are confident they'll be able to save enough to have the lifestyle they want in the future.
"They're overconfident, they're extremely optimistic if you compare them to other generations," Dan Schawbel, founder of Millennial Branding and author of "Promote Yourself," told CNBC's "Power Lunch."
"Honestly, it's not there for them. A third don't think they're going to have the same standard of living as their parents did and that's a huge problem."
President Barack Obama's decision to expand the student loan law will help to some extent, but the problem still remains, said Karen Wimbish, retail retirement director at Wells Fargo. The law caps repayments at 10 percent of income, with the balance forgiven after 20 years if the loan is not yet paid off. The president's expansion targets those who took out loans before October 2007—affecting about 5 million people.
"Today they're paying 12 percent of their income; this takes it down to 10 percent. It's not like it's a windfall," Wimbish said.
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"It's not going to take effect until next December, so we still have even more time. And tuition rates are increasing by 2 to 6 percent each year, so it is still a huge problem for them long term," Scawbel added.
The Wells Fargo study also found that a majority of millennials understand the importance of saving for retirement—80 percent said they learned that lesson thanks to the Great Recession. However, just 55 percent are doing so.
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When it comes to gender, women make less than men and are more uneasy about their financial futures.
The pay gap "has ripple effects," Wells Fargo's Wimbish said. "[Women are] less happy with their savings. They're less comfortable with the amount of debt they have. Their financial prospects don't look as positive and frankly their career opportunities look more limited."
According to the survey, the median annual income millennial men is $82,800. For women, it's $62,900.
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While 42 percent of those surveyed said debt was their biggest financial concern, 45 percent of women said they were overwhelmed by debt compared with 33 percent of men.
Millennial men are also more likely to invest in the stock market—69 percent of men said it was the best place to invest for retirement; only 49 percent of women agreed.
"Women are less confident, less engaged, less comfortable with the market. It's hard to say exactly what drives that," Wimbish said. "Earning less has something to do with it … when I have less I am less confident putting into a risky place that I perceive the stock market to be."
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—By CNBC's Michelle Fox. CNBC's Uptin Saiidi contributed to this report.