Jessica Harper, 50, pleaded guilty at Southwark Crown Court in London to taking the money from her employers using false invoices over a four-year period from 2007 to 2011 and then laundering the cash.
"Jessica Harper has today been convicted of the type of crime the bank employed her to combat," said Sue Patten, head of the Crown Prosecution Service central fraud division.
Harper, who was head of fraud and security for digital banking at Lloyds Banking Group, admitted one charge of fraud by abuse of position by submitting false invoices to claim payments totalling 2,463,750 pounds (Rs 21.2 cr).
She also admitted a single charge of laundering the money.
"Harper was expected to safeguard the financial interests of the bank. Instead, she submitted false invoices totaling more than 2.4 million pounds over a period of four years," Patten said.
Defence lawyer Carol Hawley said Harper was selling her 700,000 pounds home to repay some of the stolen cash. Harper will be sentenced at a later date.