Cilenti was born in Bradford, to Italian parents from Benevento. He worked with his girlfriend, Actress Sienna Guillory, in the 2001 film Late Night Shopping. The two were married in 2002, and they have continued to appear together in various works. In February 2011 Guillory gave birth to their twin daughters, Valentina and Lucia, named after Guillory's grandmother and great aunt, who were also twin sisters.