Wednesday's summons comes after state prosecutors, over the past few months, questioned numerous figures around Lee including his son, nephew and brother, as well as presidential secretaries who worked with him during his term, from 2008 to 2013.
Lee is also accused of using an auto parts manufacturer called DAS as a channel to establish illicit slush funds amounting to 30 billion won ($28 million) and embezzling its official funds.
South Korean presidents have a tendency to end up in prison - or meet untimely ends - after their time in power, usually once their political rivals have moved into the presidential Blue House. South Korean media said the illicitly obtained funds totaled 11 billion won ($10 million).
During the interrogation, the prosecutors also asked Lee whether his son-in-law, an executive at Samsung Electronics Co., delivered bribes to Lee's wife, Kim Yoon-ok, but Lee reportedly denied the involvement of the former first lady.
Lee arrived at Seoul District Prosecutors' Office around 9:30 a.m., the Hankyoreh reported.
Speaking in front of the Seoul public prosecutors' office, Mr Lee, 76, told journalists: "I stand here today feeling wretched. I offer my deepest apology to the people for causing worry amid times when the economy is in hardship and the situation surrounding the Korean peninsula is serious", Lee said.
"As a former president, I have many things I want to say, but I promised to myself that I must save my breath", he said.
Samsung reportedly paid six billion won ($5.6 million) in legal fees to a United States law firm on the former president's behalf.
"It would be a shame if the prosecution fails to prove Lee's wrongdoings".
With Lee condemning the accusations against him as political retaliation, the questioning session was expected to continue into the night.
The prosecution office and police beefed up security around the perimeter to prevent any possible clash.
Before he entered the prosecutors' office, Lee announced to reporters that he is in a "position of bad discomfort today". He hoped that he is the country's last president in history to be investigated by prosecutors.
Park's successors Chun Doo-hwan and Roh Tae-woo, both former army generals, spent time in jail after leaving office for bribery, treason and other charges. The probe was ended after he committed suicide in May of that year.
Former South Korean president Lee Myung-bak appeared for questioning on Wednesday over allegations he took bribes when he was in office, following months of investigations into his family and acquaintances over the graft charges.