The answer in this StackOverflow post refers to documentation saying an array will be returned; this appears to be happening after the JSONPath is evaluated (which is why appending a [0] does not work). The post also implies the answer: in NiFi, you can choose "json" as the Return Type and "flowfile-attribute" as the Destination in EvaluateJsonPath (let's say your dynamic property has key "my.attr" and a value of your JSONPath expression above), then follow that processor with an UpdateAttribute processor, setting "my.attr" to the following: ${my.attr:jsonPath('$[0]')} This will overwrite the original "my.attr" value by hoisting the value out of the array. If you need that value back in the content, you can follow this with a ReplaceText processor to replace the Entire Text with the value of "my.attr". ... View more