Officials of Japan's Imperial Household Agency say Emperor Emeritus Akihito and Empress Emerita Michiko became unwell in December.
The officials say the Empress Emerita began to show cold symptoms in mid-December, and her husband fell ill some days later.
They said the Imperial couple suffered from fever, coughing, and hoarse voices among other symptoms, but they did not have coronavirus infections or influenza.
The Emperor Emeritus and Empress Emerita recuperated toward the end of the year.
They received greetings on New Year's Day and participated in the public New Year greetings on the following day.
The officials say the Emperor Emeritus and Empress Emerita have almost fully recovered, but they are refraining from taking their daily walks.