In this work, a novel approach is presented for in-line flow compensation using a dual-Thermal conductivity detector (TCD). TCDs demonstrate a flow dependence and require a calibration at a fixed flow rate. The dual-TCD is composed of two thin-film sensors on membranes in parallel on the same chip. Both are laterally identical, but with a significantly difference on quasi-static sensitivity to the thermal conductivity of the gas by a different sample chamber. The result is a reduced flow rate dependence when differentially operated. The device is fabricated using both bulk and surface micromachining. The design, simulations, fabrication and measurements of the TCD are presented.