Born and raised in Boston, Rev. Mariama's activism began during her high school years, notably through her involvement with Project HIP-HOP, a youth organization dedicated to educating about the Civil Rights Movement and inspiring activism among young people. After college, she became the Executive Director at Project HIP-HOP, a position she held for 13 years. In 2014, she left the nonprofit field to pursue her call to ministry particularly focused on those who feel alienated from traditional church structures and theology. In 2017 she graduated with a Master of Divinity from Boston University School of Theology and was ordained as an elder in the African Methodist Episcopal Church. In 2018, she established the New Roots AME Church in Dorchester, where she serves as pastor.

In 2021, Rev. Mariama White-Hammond was appointed the Chief of Environment, Energy, and Open Space for the City of Boston. In this capacity, she led climate and energy policy, historic preservation, food justice and open space efforts. Throughout her tenure with the City, she was instrumental in embedding equity into her work, leading initiatives such as amending the Building Emissions Reduction and Disclosure Ordinance (BERDO) to establish carbon targets for existing large buildings, spearheading a city-led green jobs program for young people from environmental justice communities and overseeing a surge in historic landmark designations particular in communities of color. In April 2024 she stepped down from this position to dedicate more time to her church and community engagement work. Rev. Mariama's approach to ecological work is deeply intersectional, urging individuals to recognize the interconnectedness between issues such as immigration and climate change or the nexus between energy policy and economic justice. Her dedication has earned her numerous accolades, including the Barr Fellowship, the Celtics Heroes Among Us award, The Roxbury Founders Day Award, and the Boston NAACP Image award. Furthermore, she has been recognized as one of the Grist 50 Fixers for 2019 and one of Sojourners' 11 Women Shaping the Church.