Manjeet Mohal, 59, and Reshim Birk, 55, were on the third day of their trial at the Old Bailey when they pleaded guilty.
Mohal, an ex-employee in the finance team of IT firm Logica, pleaded guilty to two counts of the illegal disclosure.
The Financial Conduct Authority (FCA), which brought the case against the men, claimed, in May 2012, Mohal passed information he obtained from his job about negotiations on the takeover of Logica by CGI Holdings to his neighbour, Birk.
Birk has pleaded guilty to one count of insider dealing, admitting he used the information he gained to purchase shares in Logica two days before the takeover was publicly announced, pocketing over £100,000 in profit in the process.
"We are determined to do whatever is required to curb insider dealing and other market abuse to protect both the investing public and market integrity and we will continue to prosecute cases and hold wrongdoers accountable where there is sufficient cause," said Mark Steward, executive director of enforcement and market oversight at the FCA.
The duo are due to be sentence on 13 January next year.
No evidence has been offered against a third defendant, Surinder Sappal.
The FCA's wider investigation into the Logica dealings has already resulted in a 10-month prison sentence for Ryan Wilmott, a former senior manager at Logica, for two counts of insider dealing and a £35,212 fine for former accountant Kenneth Carver for dealing in Logica shares on the basis of inside information.