Exhibit 99.1 Mercantile Bank Corporation Announces Strong Third Quarter 2025 Results Growth in net interest income and certain noninterest income categories and continued strength in asset quality metrics and capital measures highlight the quarter GRAND RAPIDS, Mich., October 21, 2025 – Mercantile Bank Corporation (NASDAQ: MBWM) ("Mercantile") reported net income of $23.8 million, or$1.46 per diluted share, for the third quarter of 2025, compared with net income of $19.6 million, or$1.22 per diluted share ...