Jessica Mang, 30, and Christina Weckwerth, 44, were being two-timed by banker Thomas Ammann when he told both to buy shares in a company about to be taken over.
Ammann, who worked for Japanese investment bank Mizuho International, was advising on the deal and had access to sensitive inside price information.
When the deal went through, Weckwerth made €1m (£805,000) and Mang, a chiropracter from Surrey, made £29,000. Ammann took half of the profits from each.
Yesterday, a jury accepted both women did not know they were trading on illegal information and cleared them following a trial at Southwark Crown Court.
The women will not have to pay back the money.
Ammann had already pleaded guilty to two counts of insider dealing and two counts of encouraging insider dealing and is facing jail.
Financial Services Authority enforcement and financial crime director Tracey McDermott said: “As an approved person Ammann knew he could not deal using the inside information he had without arousing suspicion but he thought that by getting his girlfriends to trade instead they could avoid being caught.
“He was wrong, and he now faces the consequences.”
The FSA said it made no criticism of Mizuho International.
A Mizuho spokesperson said: “The FSA has not expressed any concern about Mizuho International or its systems and controls.”
Ammann had been working on Canon’s takeover of Dutch photocopier firm Oce in late 2008 and early 2009 and dating both of the women when he got them to snap up shares in Oce.
Once the firm was bought both sold their shares for profit.
“The charges against Weckwerth and Mang were serious and we considered that the evidence provided a proper basis to put the case before a jury for them to decide. Criminal prosecutions are integral to the FSA’s long term strategy of delivering credible deterrence and combating city wrongdoing,” McDermott said.