William Blair equity analyst Robert Napoli upgraded Green Dot Corp. to "outperform" from "market perform" following the company's strong second-quarter earnings results and continued "momentum" in organic growth.

Napoli wrote that the company exceeded his adjusted EPS estimate by 15 cents and saw organic growth accelerate to 12%. In addition, the company raised its guidance for 2017, resulting in a raised estimate from him.

"On an organic basis, active cards were 1% below year-ago-levels, and recent trends suggest the company is well on its way to achieving year-over-year card growth by early 2018," Napoli wrote.

Napoli stated that the company's new products launched in the second half of 2016 are "well above" legacy products and that the company's improving customer mix and growth of direct deposits presents a large opportunity for the company.

William Blair now estimates the company's 2017 EPS will be $2.09, up from $1.94. It also increased its 2018 estimate to $2.45 from $2.27 and introduced a 2019 estimate of $2.77 per share.

Napoli's price target is $55 per share.