The Grand Rapids, Mich., company earned 77 cents a share against 61 cents in the year-earlier quarter. Analysts surveyed by FactSet were expecting 63 cents.
Mercantile Bank shares finished up 3.9% at $34.12, near their 52-week high of $35.43, set in late January.
The shares are trading around 12.5 times the past 12 months of earnings; the dividend yield is 3.2%.
Total revenue in the quarter rose nearly 11% to $38.3 million. Net interest income, the difference between what a bank takes in on loans and pays out in deposits, climbed nearly 6% $31.6 million.
The net interest margin narrowed 16 basis points to 3.71%. The figure was a tick higher than the FactSet-derived consensus estimate of 3.7%.
Assets not earning interest were 0.1% of total assets at Sept. 30. "The level of past-due loans remains nominal," the company said in a statement.
At Sept. 30, the company's assets were $3.71 billion, up 12% from a year earlier.