The Romanian former world number one had her four-year doping ban cut to nine months by the top court for global sport last week, making her eligible to return to competition immediately.
"Feels like I never left," Halep wrote in an Instagram story with a winking emoji.
"First day back, thank you @miamiopen."
Halep, a former Wimbledon and French Open champion, was suspended in October 2022 after she tested positive for roxadustat - a banned drug that stimulates the production of red blood cells - at the US Open that year.
She was also charged with another doping offence last year due to irregularities in her athlete biological passport (ABP), a method designed to monitor different blood parameters over time to reveal potential doping.
Halep, who vigorously denied the charges against her, said that she would most likely have been compelled to retire if the initial four-year ban was maintained.
The Miami Open runs from March 17th to 31st.
