The Blurred Lines singer took the stand in his ongoing copyright trial against Gaye's children and told a court in Los Angeles he told "a little white lie" to reporters who asked him about the conception of his 2013 hit, which bears a striking resemblance to late soul legend Gaye's tune.
Thicke backtracked on radio and magazine interviews he gave in 2013, during which he claimed that he proposed to Williams that they write something like Gotta Give It Up.
He told the federal jury that he was drunk and high on drugs during those interviews, and that he was simply attempting to take credit for a part of the song.
He said, "It felt like a little white lie that wouldn't hurt his (Pharrell) career and boost mine."
The Gaye children have used the interviews as part of their argument Thicke and Williams heavily borrowed from their father's song and therefore infringed on their copyright.
Under questioning by his own attorney, Thicke performed hits by U2, Michael Jackson and the Beatles to prove that many classic songs shared similarities.
Also taking the stand on Wednesday was Gaye's ex-wife, the mother of one of the plaintiffs, who testified she noticed the similarities between Blurred Lines and her former husband's song as soon as she heard the 2013 hit.