The executive revealed in an email that the company's same-store sales had risen about 6 percent in the quarter to date, J.C. Penny said on Tuesday.
J.C. Penney said it expected same-store sales to rise by about 3.5-4.5 percent in the first quarter, after adjusting for Easter falling in March this year.
The company, which is expected to release results in mid-May for the February-April first quarter, declined to identify or comment on the executive in question.
Its same-store sales growth has slowed over the past three quarters from 6.2 percent in the first quarter of 2014.
The company's shares fell 3 percent to $9.12 on the New York Stock Exchange.
By Yashaswini Swamynathan; editors: Kirti Pandey and Simon Jennings.