The former head and founder of ShelterBox in Helston has been arrested on suspicion of committing fraud and money laundering offences.
It is believed police raided the home of Tom Henderson, his son John and another man, seizing items believed to be computers and documents.
Mr Henderson was dismissed for alleged gross misconduct from ShelterBox in July 2012 and is appealing his dismissal at an employment tribunal.
It followed concerns by the charity around a possible conflict of interest with a business they believed his son was involved in, which was about to receive a major order.
In April Mr Henderson launched a rival disaster relief organisation, The Jane Henderson Foundation, set up in memory of his wife, who passed away in August.
"A 62-year-old man from Helston, a 33-year-old man from Hayle and a 40-year-old man from Beaminster in Dorset have all been arrested on suspicion of committing fraud and money laundering offences," a police statement said.
Three search warrants were executed on Wednesday, by officers in connection with an on-going fraud investigation, it added.
ShelterBox said it had been "made aware by Devon and Cornwall Police that a former member of its staff has been arrested as part of investigations into allegations of fraud and money laundering offences".
"The employee in question was dismissed from his role with ShelterBox in July 2012, and is no longer connected with the charity," it said.
"We are confident that his arrest is in no way related to ShelterBox's current activities. ShelterBox is co-operating fully with Devon and Cornwall Police in support of their enquiries."
Mr Henderson founded ShelterBox in 2000 and was appointed OBE in 2010 for services to humanitarian aid.
