New figures from An Post show that it delivered 1.74 million parcels in the five week lead-up to Christmas 2017 - an increase of 27% on the same time the previous year.
An Post said that was the highest number of parcels ever delivered by the company during a Christmas season.
It noted that parcel volumes from Amazon alone showed an increase of more than 30% on 2016.
Irish brands including Arnotts, Brown Thomas, Gifts Direct and Smyths Toys were among its biggest parcel customers, alongside international brands Zara, H&M and IKEA.
An Post also said that its mail volumes performed better than expected in December, falling by just over 6% in the month.
It said this was in line with global trends of declining mail volumes.