Snapchat isn't just for millennials anymore.
At least that's what investment research group Jefferies is telling clients in a note that highlights where the app's user engagement growth has risen of late.
"In our proprietary survey we were surprised to see that Snapchat's engagement is growing in older demographics," equity analyst Brian Fitzgerald wrote in Monday's note. "We found that usage has increased across the platform, but the most improvement has been seen in users aged 25+."
Forty-one percent of users ages 25 to 34 used the app more often today than during Jefferies' first survey last June. Forty-four percent of the 34 to 44 demographic use Snapchat more now, the firm said.
Jefferies' survey includes 1,000 internet users based in the U.S., ages 18 to 45, who use both Snapchat and Facebook products, the note said.
The Snap-owned company has been growing with "older," "broader" and more "monetizable" demographics, Fitzgerald said. The now-public company needs to continue its growth to perform well over its competition.
"Our findings suggest Snapchat's engagement has actually increased, but interestingly not at the expense of [Facebook's] Instagram – suggesting it is not a zero sum game," the firm added.
Over the next year to 18 months, Snap's "biggest driver" will be its ability to leverage a "massively engaged user base" via its growing advertising offerings, Fitzgerald said. Lately, "Snap has improved the ability to target with direct response ads as well as increased the number of gamified ads which have much longer brand engagement."
Jefferies maintains a buy rating on Snap, which was initiated in March following Snap's initial public offering, and a price target of $30 per share. Snap closed at $20.19 on Thursday.
Shares of Snapchat parent company Snap were down slightly in premarket trade Monday, trading above $20. That's down from the stock's all-time intraday high of $29.44, according to FactSet.
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Disclosure: CNBC parent NBCUniversal is an investor in Snap.