Two solutions: Before that, I believe, you constructed that(csv) value using groovy/any script. If so, try understanding the following: inputString = '{"firstName":"John","lastName":"Legend"}' new JsonSlurper().parseText(inputString) will return MapRecord[{firstName=John, lastName=Legend}]. So, before writing the flowFile, use new JsonOutput().toJson(new JsonSlurper().parseText(inputString)). This will give {"firstName":"John","lastName":"Legend"} in Json Format(not String) If that wasn't the case, try replacing 'MapRecord[{' and '}]' with empty string and split the text with "," as delimiter and for each, split again with "=" as delimiter. ... View more