Last week, Einhorn sued Apple for allegedly sitting on a cash pile.
American hedge fund manager, David Einhorn has increased his stake in Apple by about 50% in the fourth quarter of 2012, according to a regulatory filing.
Financial Times said that Greenlight raised its holdings in Apple by 46% to 1.6m shares, including shares covered by call options.
The filings do not reflect any trades that have been made since the beginning of 2013..
Last week, Einhorn sued Apple, demanding the company must disburse more of its $137bn cash pile to shareholders.
He alleged that Apple did not take measures to ensure that its shareholders receive the benefits of the company's success.
Recently, a US judge agreed to a request by Apple to speed up the lawsuit schedule filed by Einhorn.
Earlier this week, Apple CEO, Tim Cook, described the Greenlight lawsuit against the company as a "silly sideshow" and a waste of time.
Apple has also been sued by a Pennsylvania investor, Brian Gralnick, in order to stop the company from holding a shareholder vote on two proxy proposals.
Apple reported a 18% rise in its revenue to $54.51bn for the fiscal first quarter of 2013, compared to $46.33bn for the same period last year.