As a Mainframe Developer, you'll typically be responsible for designing, coding, testing, and maintaining programs on IBM mainframe computers using languages like COBOL, JCL, and DB2. Your day-to-day tasks might also include troubleshooting production issues, performing system upgrades, and collaborating with cross-functional teams to implement new features or enhancements. You'll often work within larger IT departments for industries such as finance, insurance, or healthcare, where mainframes play a vital role in core business operations. This collaborative environment offers opportunities for growth into technical lead or architect positions as you gain experience.