For career/major related employment, UMass Amherst uses Handshake, a free job board and internship platform that employers can use to post a job or internship. This allows students and recent alumni to search and easily apply according to the directions you specify in your job ad.
Handshake Best Practices
Student Job Board
For part-time and seasonal work opportunities, the UMass Student Job Board is available for local employers to advertise non-major/non-career related work opportunities for students.