Year-on-year property prices have risen by 8.2% across the country, which represents the strongest annual growth in 15 years.
In addition, the data noted that a third of local authorities recorded a double-digit percentage increase in property prices.
Overall, 18 local authorities reached a new record high in the average house price.
Detached house prices were 11% higher than a year ago, the greatest rise of all property types.
On an annual basis, average house prices in Anglesey saw the largest uptick, rising by 16% to £237,782.
Conwy followed, noting a 13.7% increase, resulting in average house prices reaching £224,068.
Merthyr Tydfil recorded the strongest rise on a quarterly basis, rising by 18.2% to £147,687.
Bridgend recorded the lowest annual rise, increasing by 1.6%, and the region also noted the only decline on a quarterly basis, dropping by 4.1%.
As a result, average property prices in Bridgend were £183,721.
Overall transactions were down by 21% in 2020 compared to 2019.
Tom Denman, chief financial officer at Principality Building Society, said: “The strength of the housing recovery in the second half of 2020 is striking.
“This reflects both the stimulus provided by the Welsh government in terms of the time-limited land transaction tax holiday, the pent-up demand which built up during the first lockdown, and the race for space to buy bigger properties with larger gardens.
“In Q4, all local authority areas were reporting house prices higher than a year earlier.
“This increased demand has been driven by increased savings in many households during the lockdowns coupled with continued historic low mortgage rates.
“There has probably been some additional demand from buyers across the border with England, with house prices more affordable in Wales in relative terms.
“The recent UK HM Treasury review of independent forecasts for 2021 showed wide divergences in house price expectations for the year. With so many unknowns it is impossible to offer a forecast with any reasonable accuracy.
“However, once there is more clarity on the containment of the virus and on the full re-opening of the economy, it will become easier.”
