Venmo is just one page in PayPal's mobile payments portfolio, though — the company, across all of its P2P platforms, moved $27 billion in the last quarter alone — so Zelle hasn't proven to be a threat yet.
"We have tremendous momentum behind our broader [person-to-person segment]," Ready said. "As other players come into the space, our growth has only accelerated."
New players in the sector, Ready said, contribute to broader user education, bringing new users into the ecosystem and, in many cases, sending them to the established incumbents.
Zelle, though, stands to capitalize on an older demographic less concerned with social features and more concerned with security. It's also no-fee, where the Venmo and Cash apps take a small percentage for certain transactions.
The rollout has been gradual and thus far quiet, as individual banks integrate Zelle into their banking apps.
The adoption challenge for Zelle is a unique one. Banks don't have to educate users on the functionality of Zelle or convince them to download the service. Instead they have to inform users they already have Zelle on their phones, in their banking apps.
The service has launched a massive multiplatform ad campaign and plans to air more 3,000 TV ads in the first quarter featuring Daveed Diggs, star of the musical "Hamilton."
The goal is to "broaden digital payments from millennials to mainstream," a Zelle spokesperson told CNBC, but that doesn't inherently eliminate competition from third-party processors like PayPal and Square.
Adding users to Zelle doesn't mean taking them off PayPal, according to several analysts. The use case for Venmo differs from that of Zelle — the same user is likely to send a few dollars through Venmo, but a few thousand through Zelle.
"Zelle represents more of a threat to cash and checks rather than Venmo," Evercore analyst David Togut said.
Correction: An earlier version of this story mistakenly said that Zelle had surpassed PayPal's P2P volume.