Jo March, the second-oldest March sister, exhibits a tomboyish nature and an outspoken personality fueled by a strong passion for writing, coupled with a volatile temper that often sparks conflicts, especially with her youngest sister, Amy. Her defining physical act involves cutting off her blonde hair and selling it to finance her mother's journey to their wounded father, a Civil War chaplain.

She shares household responsibilities with her sisters and works as a companion to Aunt March, assisting with daily care. Jo shares an especially close bond with her shy sister Beth, acting as her protector. Her significant friendship with their wealthy neighbor, Laurie, includes her rejection of his eventual marriage proposal.

Key developmental events include volunteering at a field hospital in her town during the war, demonstrating her growing social responsibility. Her protective instincts are prominently displayed when Beth contracts scarlet fever from a poor German family while their mother is away; Jo remains deeply involved in Beth's care throughout the illness.

Her literary aspirations drive subplots, such as participating in editorial meetings for a family newspaper produced in the attic. Later, she writes sensational stories for weekly tabloids, encouraged by Professor Fritz Bhaer to pursue more serious writing. This mentorship evolves into a romantic relationship, culminating in their marriage.

The narrative concludes with Jo embracing motherhood, raising two sons named Rob and Teddy. Her journey reflects a transition from impulsive outspokenness to a more measured maturity, balancing her creative ambitions with familial and social commitments.