Johnson clocked 3 minute 35.24 seconds to finish second behind Joshua Thompson of United States at the Olympic Stadium in Berlin.
With his own national record shattering effort, Jinson also qualified for the World Championships to be held in Doha from September 28 to October 6.
The World Championships qualifying time is 33 minutes 36 seconds.
ISTAF Berlin is a part of the IAAF World Challenge meetings, the second tier of global one day athletics events.
It is the penultimate leg of the IAAF World Challenge meetings this year.