The publisher is said to have a monthly women's "body and mind" title and a weekly magazine scheduled for launch later this year.
Over the past year, NatMags has used Clemmow Hornby Inge for all its advertising. The agency launched the ACP-NatMag celebrity weekly Reveal in October. Last month, CHI created the first campaign for Cosmopolitan since it launched in 1972.
However, it is thought the publisher is considering using at least one other agency for its large portfolio of brands.
Last year, NatMags developed its business via several joint ventures.
In a link-up with Australian Consolidated Press, it now publishes two magazines, Best and the recently launched Reveal, under the ACP-NatMag name.
It also tied up with Rodale, creating NatMag-Rodale, to publish Men's Health and Runner's World.
Duncan Edwards, NatMags' recently promoted chief executive, oversees the entire company in the UK.
A NatMags spokeswoman said: "There are no imminent plans to appoint any agency and we're not in discussions. We are looking at new product development across the business but there are no announcements to be made imminently."