In the three and half years since her arrival, Engine said Jasinski has been responsible for increasing its success in new business, organic growth and its profile.
For example, Engine has become the most successful agency on the government roster and won integrated accounts with E.ON and the Payments Council.
Debbie Klein, the chief executive of Engine UK, said: "Nina is a great talent and special kind of CMO and we are sad to see her go.
"We are proud of what she and her team have achieved for Engine and will announce shortly the person who will continue this upward growth curve.
"We have been talking to Nina about her desire to do something different for some time now and wish her well."
Jasinski said "I’ve had a great time at Engine but feel now is the right time to do something different and am exploring interesting ideas with both companies and individuals"
She will leave the agency in May.
Jasinski joined Engine from EDC UK, the parent company of Dare and Elvis, where she was group marketing director.
She has also worked at Rainey Kelly Campbell Roalfe/Y&R, Leo Burnett London, Wunderman, Miles Calcraft Briginshaw Duffy and a seven year stint at Partners Andrews Aldridge before it was part of Engine.