Ramos succeeds Zico, who was sacked after a series of poor results.
"I love new challenges. We are looking forward to helping the team realise their potential in Europe and working really hard over the next three months," the 54-year-old Ramos said in a statement on his personal website.
CSKA spokesman Sergei Aksyonov confirmed the appointment, telling reporters: "Juande Ramos was introduced to the team at today's practice."
Ramos has signed with CSKA to the end of the year.