Nigella's former aide Elisabetta Grillo, 41, said she had found a packet of white powder in a toilet in the home Nigella shared with her former husband, John Diamond.
She told Isleworth Crown Court that she had also seen rolled-up banknotes and credit cards with white powder on them.
Asked if she had ever seen the celebrity cook taking drugs, Grillo said "No".
Grillo, who worked for Ms Lawson as an au pair, said she did not confront the 53-year-old about the issue as she did not want to embarrass her.
Celebrity cook Nigella Lawson said she was "disappointed but unsurprised" after her two former personal assistants were cleared of fraud.
The revelations that emerged in the fraud trial of two former aides to Nigella Lawson are unlikely to damage the TV chef's meteoric career.
Nigella "let the children smoke weed," an ex-PA has alleged, admitting she had wanted to drop drug claims out of sympathy for her ex-boss.