Hearns was born in Columbus, Ohio. She grew up in a single-parent home with two sisters. She struggled being raised as a "little black boy who was existentially trapped in a boy’s body, but was definitely very much so female." Before discovering that she was transgender, she thought she was gay, and dealt with suicidal thoughts as she thought being gay was a sin.
In 2013, Hearns co-founded the Black Lives Matter Global Network. As a strategic partner and organizing coordinator, she helped develop policy for the network, including the 2016 policy platform "A Vision for Black Lives". She co-organized a National Day of Action in 2015 to bring attention to the black trans women who were killed that year.
Hearns founded The Marsha P. Johnson Institute, where she serves as Executive Director. The mission of the institute, which is set to launch in Spring 2018, is to train and support black trans women and gender-nonconformingfemmes.
In February 2017, Hearns, along with other trans activists, criticized the pussyhat that had become a symbol of the 2017 Women's March, stating that the movement needs to be truly intersectional and consider the "anatomy of all people".
In August 2017, Hearns and fellow organizers at the Marsha P. Johnson Institute, along with other trans activists, spoke out against an episode of The Breakfast Club radio show where remarks were made about trans women. Comedian Lil Duval joked about killing a sex partner if she turned out to be transgender, and host Charlamagne Tha God, while noting that killing a trans person was a hate crime, stated that women not disclosing their trans status were "taking away a person's power of choice" and "should go to jail or something". Hearns and her colleagues circulated a petition calling for the program to be taken off the air.
On September 30 2017, Hearns spoke at The March for Black Women in Washington, D.C. about the sisterhood between transgender and cisgender black women.