Accompanied by his family members and top party office-bearers, Thackeray left his residence under a tight police escort to the ED headquarters in Ballard Estate in south Mumbai.
Two days ago, in a statement, Raj Thackeray had declared that he would honour the summons by the ED as he had always done in the past.
Earlier, MNS spokesperson and other activists were detained from Dadar and whisked off to the nearby Shivaji Park Police Station to pre-empt any untoward incident.
Strongly protesting his detention, Sandip Deshpande termed it as "high-handed action" by the police.
Other activists protested silently by sporting black tee-shirts with the slogan "EDiot Hitler" painted on them, as thousands of supporters came to Mumbai from all over Maharashtra to express solidarity with their chief.
Late on Wednesday, the MNS activists were served police notices warning them against creating any law and order issues on Thackeray's appearance before the ED.
The police have taken measures to maintain law and order in the city. Barricades have been deployed, traffic diversions made, and a large posse of personnel and even a dog squad have been kept ready. Prohibitory orders have been issued in some key pockets to tackle the situation.
Thackeray has issued at least two direct appeals to all his followers to remain calm despite any provocation, keep away from the ED office, and desist from any form of agitation or violence.
However, his estranged cousin and ruling ally Shiv Sena President Uddhav Thackeray on Wednesday indirectly backed Raj Thackeray by saying that nothing would emerge from his (Raj's) interrogation by the ED.
"I don't think there will be any outcome of his (Raj's) investigation by the ED," Uddhav had said.
Raj Thackeray's former business partners Unmesh Joshi son of former Lok Sabha Speaker Manohar Joshi and Rajan Shirodkar, have already been grilled by the ED in a case pertaining to the IL&FS imbroglio.
On Wednesday, agitated by the ED summons to the MNS Chief, a young party activist committed suicide by setting himself on fire.
( With inputs from IANS )