The planning business was previously split between WPP's Maxus and PHD.
"In the course of renewing contracts with our advertising agencies, we have made a decision to have one global media planning agency, which will be PhD," a spokeswoman said in an email. "We are currently working on a transition timeline. We anticipate completing the transition by spring."
Maxus continues to handle SC Johnson media buying, the spokeswoman said.
The change follows the Racine, Wisc.-based company's recent shift toward Omnicom's EnergyBBDO, which picked up brands including Windex and Drano from WPP's Ogilvy & Mather in 2014.
SC Johnson spent $228 million on domestic measured media in 2013, according to Kantar Media's last full year of available spending data.