The appointments are the first since Neil Godber was promoted to JWT's head of planning last month ahead of the departure of Tracey Follows, the chief strategy officer and executive partner at JWT.
McCreary joins as a planning director from Carat where she was a digital strategy director, leading social and digital strategy on accounts such as British Gas, Disney and Bodyform.
Goodwin joins as a data planner. He comes from The Specialist Works and has also previously worked at Sky IQ.
Godber said: "The appointment of more specialist planners is a reflection of our ambitious plans for a wide range of planning skills in the department.
"This is crucial in our ability to continue to deliver pioneering ideas based on intelligence, executed through campaigns fit for the digital age."
Follows leaves JWT later this month.