Mariellen Bello is a graduate of Ursinus College and a graduate of the Temple School of Law. Mariellen worked in the Labor and Employment Law department of Montgomery McCracken Walker & Rhoads from 1989 to 1996, and during that time, she handled numerous employment litigation cases. She has worked for this firm since 1997, practicing primarily in the areas of employment law counseling, litigation, and employee benefits. She has provided training to numerous organizations regarding avoidance of racial, ethnic, and sexual harassment in the workplace.

Mariellen is a member of the state bars of Pennsylvania and New Jersey, and numerous federal district courts.