Exhibit 99.1 Isabella Bank Corporation Reports First Quarter 2025 Results MT. PLEASANT, MICHIGAN — April 17, 2025 — Isabella Bank Corporation (OTCQX: ISBA) (the "Company" or "we") reported first quarter 2025 net income of $3.9 million, or$0.53 per diluted share, compared to $3.1 million, or$0.42 per diluted share in the same quarter of 2024. The non-GAAP measure of core earnings in the first quarter 2025 totaled $4.3 million, or$0.57 per diluted share, compared to $3.1 million, or$0.41 per diluted share ...