He will relocate to London from his native Brazil to service the account.
Unilever is Lowe and Partners’ biggest client globally and has been with the network for more than 50 years. Lowe and Partners handles the Persil brand in more than 30 markets and also works with brands including Magnum, Clear, Signal, Rexona and Knorr.
Okada is a former executive creative director at Publicis Spain and chief creative officer at McCann Brazil.
Helen Bell, chief operations officer at Lowe for Unilever, said: "Alexandre has the international credentials that are pivotal to a role like this. He understands the brand on a global level, which has always been key to its success.
"We look forward to seeing how he will help us take the brand forward."
Okada added: "OMO and Persil are emblematic brands that, despite being global, are perceived as local and are loved as such in every country they are present. Lowe and Unilever have built together a great story of success and it is a great challenge to work for brands with such amazing potential."