Following the result, India are set to receive $1 million prize money from the International Cricket Council.
Meanwhile, New Zealand finished as the second placed team.
Here's what Kohli said about this achievement.
2018-19 in Tests
India have had a dominant year in Test cricket
Considering India's performance in Test cricket this season, the Virat Kohli-led side started with a dominating win against Afghanistan.
It was followed by a 2-0 win in the Windies at home.
Although India suffered a 4-1 loss in England, it was immediately rectified when Team India won 2-1 in Australia.
Notably, it was their first-ever Test series win Down Under.
Only the best can prosper in the format: Kohli
Indian skipper Virat Kohli said, "Retaining the ICC Test Championship Mace once again is something we are all really proud of. Our team has been doing well across formats but it gives us extra pleasure to come out on top of the Test rankings."
Eyes on World Test Championship
Kohli also said that he is proud of the depth in the current Indian squad.
"Our team has a lot of depth and I am sure this will stand us in good stead once the ICC World Test Championship commences later this year. That is again something we are really looking forward to as it adds more context to Test match cricket," added Kohli.
India to meet Windies, South Africa, Bangladesh and New Zealand
India would look to continue their dominant performance as they lock horns with four countries this term.
It starts in West Indies in July 2019 with two Tests.
It would be followed by a three-match home series against South Africa in October. Bangladesh would then visit India in November.
It ends in New Zealand with two Tests in February 2020.