The Press Trust of India news agency says Sayed Zabiuddin is suspected of tutoring the gunmen in the Hindi language and relaying directions during the three days of shootings.
The agency says he was arrested at New Delhi's international airport four days ago.
Zabiuddin is an Indian national who also goes by the name Abu Hamza. Authorities say he is a member of the Pakistan -based Lashkar-e-Taiba Islamic militant group.
Indian authorities say they learned of the suspect while interrogating the lone Pakistani gunman who survived the 2008 attack.
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