England Test coach McCullum cleared of anti-corruption breach
Reports said the New Zealander had stepped back from his commercial role with 22Bet, a Cyprus-registered bookmaker for whom he has appeared in several online advertisements.
Last month, a video was posted on McCullum's official Facebook page showing him promoting the company's Indian Premier League markets ahead of the season.
Players, coaches and officials taking part in or encouraging betting on matches is prohibited under the ECB code, prompting the governing body to announce it was "exploring" McCullum's links with 22Bet.
But the ECB announced on Wednesday that McCullum had done nothing contrary to the code, which does not prevent players or officials from becoming brand ambassadors for betting organisations.
An ECB spokesman said: "Discussions have been ongoing with Brendon over the last few days, and the matter has been considered from an employer and regulator perspective.
"We can confirm that no further action will be taken."
It is understood McCullum, who has won 10 of 12 matches and been credited with revolutionising England's Test side alongside captain Ben Stokes, will consult with the ECB before undertaking any future work with 22Bet.