In 2014 she opened her own law firm, after serving as Company Secretary and Head of Corporate Affairs and Projects (Legal) of Cable & Wireless Jamaica Limited.

[3] Being highly committed to public service and volunteerism, Johnson Smith served as a member of the Advisory Board of the iLead Education Reform Project sponsored by the Jamaica National Foundation.

She has successfully tabled Parliamentary motions regarding public sector governance, re-integration of teen mothers in the formal school system, and the review of laws related to violence against women, children, the elderly and persons living with disabilities.

Johnson Smith has expanded the number of countries with which Jamaica has established diplomatic relations and promulgated a Consular Manual to improve service delivery to citizens overseas.

[10] As Leader of Government Business in the Senate, in her first term of office, she led over 110 debates including the passage of 69 statutes and 48 resolutions across government portfolios - ranging from the establishment of states of public emergency to curb the country's inordinately high crime rate; reforms to the justice system and the fight against human trafficking; the strengthening of laws addressing AML/CFT frameworks; the modernization of corporate, partnership and trust laws, as well as intellectual property frameworks; data protection; public procurement; road safety; building and land titling.

At the 2022 Commonwealth Heads of Government Meeting held in Kigali, Rwanda, Jamaica's candidate - Johnson Smith - narrowly lost to the incumbent, reportedly with a result of 27 votes to 24.