According to media reports, Tharoor proposed to marry Sunanda, a girl from a Kashmiri family. Trained as a beautician, Sunanda runs a spa and has lived in Dubai.
Sources close to the 54-year old Tharoor declined to comment on the reports, urging the media to respect his privacy.
"He will announce whatever, when he has something to announce," a source said.
The minister is said to be undergoing a legal separation from his second wife Christa Giles, a Canadian civil servant who works with the United States on disarmament issues.
Earlier, Tharoor was married to a academic Tilottama Mukherji, whom he knew from his school days in Kolkata.