"The CAS Panel in charge of the matter has reduced her period of suspension, by nine months, from two years to fifteen months, beginning on 26 January 2016," CAS said in a statement.
Meldonium was only added to the World Anti-Doping Agency (WADA) list of banned substances on January 1, 2016.
Earlier in the day, Russian Tennis Federation Shamil Tarpischev said that Maria Sharapova will be able to take part in competitions from April 26 next year after the reduced ban runs out.
Sharapova reacted positively to the ruling, reiterating that she took responsibility for unknowingly taking a banned substance and blaming the ITF for failing to provide timely information on newly banned substances to its members.
"I also learned how much better other Federations were at notifying their athletes of the rule change, especially in Eastern Europe where Mildronate is commonly taken by millions of people… Now that this process is over, I hope the ITF and other relevant tennis anti-doping authorities will study what these other Federations did, so that no other tennis player will have to go through what I went through," the tennis champion wrote on her Facebook page.