Because Lab Girl is a memoir, its characters are significant people in Jahren's own life journey.

Hope Jahren

The central character of the memoir, not surprisingly, is Jahren, as she unveils the intellectual, emotional, and very personal journey she has taken in pursuing science, discovery, growth, healing, and success. Jahren shares not only academic revelations but also deeply personal understandings of herself; she openly discusses her struggles with overwork, depression, pregnancy, and bipolar disorder. Throughout her memoir, Jahren shares her passion for plants as a geobiologist, as well as her passion for a meaningful life of discovery.

Hope Jahren's Parents and Family

Jahren shares glimpses into her Scandinavian family, including discussion of members tracing back to her great-grandparents. Primary, however, are her discussions of her relationships with her parents. While growing up, Jahren's parents are strict, but they encourage the pursuit of science and education. As a child, Jahren is allowed to explore science in her father's laboratory, as he is a professor of science classes at a local college. She also plants and tends vegetable and flower gardens with her mother.

Bill Hagopian

A main character in the memoir is Bill Hagopian, Jahren's brilliant lab partner and colleague and her steadfast friend for many years. She recounts the many adventures she takes with Hagopian and the ways they grow from their shared explorations.

Clint Conrad

Jahren also writes about meeting her husband, Clint Conrad, a fellow scientist, and about her happiness with him.