A more cautious and uncertain outlook for e-commerce spending at PayPal Holdings Inc. propelled a near-record selloff in shares of the financial-tech company on Tuesday.

PayPal said Monday that it was reducing its forecast for online payment volumes and revenue in the fourth quarter, citing factors including supply-chain issues upending holiday sales, reduced appetite for travel and idiosyncratic challenges at eBay Inc. Preliminary guidance the company provided about how it expected to perform in 2022 also came in lower than...

A more cautious and uncertain outlook for e-commerce spending at PayPal Holdings Inc. propelled a near-record selloff in shares of the financial-tech company on Tuesday.

PayPal said Monday that it was reducing its forecast for online payment volumes and revenue in the fourth quarter, citing factors including supply-chain issues upending holiday sales, reduced appetite for travel and idiosyncratic challenges at eBay Inc. Preliminary guidance the company provided about how it expected to perform in 2022 also came in lower than analysts anticipated.

Those revelations contributed to PayPal’s stock falling 10% to $205.42 on Tuesday, its second-worst trading day since spinning out of eBay in 2015. After more than doubling last year and hitting an all-time high as recently as July, PayPal shares have now declined 12% since the start of 2021.

Investor sentiment around PayPal turned more negative last month when news leaked that the company was in talks to buy social-media platform Pinterest Inc. Shareholders balked at the potential $40-billion-plus deal, prompting PayPal to halt its pursuit.

Chief Executive Dan Schulman tried to reassure investors that the company wasn’t looking to do big deals at any cost. “We haven’t done a single large acquisition because they haven’t met any of our hurdles,” Mr. Schulman said on a conference call with stock analysts on Monday. “I’m not saying that we might never ever do that, but, you know, it’s not a likely event.”

PayPal’s third-quarter per-share earnings, also announced Monday, exceeded consensus estimate of analysts polled by FactSet. But the company’s revenue and payment volume were lower than expected due to weaker back-to-school spending and pressure from eBay, executives said. EBay has been migrating from PayPal to a separate, primary payment-processor since last year.

The end of its contract with eBay also freed PayPal to pursue partnerships with other big online marketplaces, including one it announced this week between its Venmo unit and Amazon.com Inc. Starting next year, Venmo users will be able to pay for their Amazon purchases with their Venmo accounts. PayPal has struggled to make money from the money-transfer app, but the Amazon deal could help improve Venmo’s profitability.

“Dan and I both appreciate that the investor community probably is getting tired of us talking about eBay and eBay results—but arguably not more so than we are—but this is the other side of that coin,” PayPal finance chief John Rainey said on Monday’s conference call.

Write to Peter Rudegeair at Peter.Rudegeair@wsj.com and Ben Eisen at ben.eisen@wsj.com