Alexander’s legal practice is defined by her background in medical toxicology and environmental health, a technical foundation she developed while working at the Stanford Research Institute. This expertise allows her to navigate the complex causation required in product liability and catastrophic injury litigation. Her firm, Mary Alexander & Associates, P.C., notes that her approach prioritizes the human element of cases, ensuring that survivors of preventable harm are heard against defendants with significant institutional resources.

Her recent portfolio includes securing a $2.25 million settlement in a sexual abuse case against the Castilleja School Foundation and playing a pivotal role in the Archdiocese of Los Angeles clergy abuse litigation, which resulted in settlements exceeding $1.5 billion. Beyond individual representation, Alexander served as liaison counsel in the Ghost Ship Fire litigation, successfully securing over $32.7 million for victims and their families while overcoming governmental immunity defenses. Her career also features a central role in the two-decade-long California lead paint litigation, which culminated in a $305 million settlement for hazard remediation. A former president of the American Association for Justice, Alexander remains one of the state's most prominent figures in plaintiffs' law.