Cowell, 54, who has four-month-old son Eric with Silverman, shelled out at least USD 10 million for the new three-bedroom suite on East 78th Street, reported the New York Post.
"They closed on a luxury apartment on the Upper East Side, close to where Silverman's other son, Adam, 7, lives with his father, Andrew Silverman," a source said.
It is not clear which apartment the couple bought, but a three-bedroom in the building was recently listed for USD 10.8 million.
Cowell and Silverman have been house-hunting for several months. With him recently returning to the judging panel on the UK's 'X Factor', it is expected the couple plan to divide their time between New York and London.