There are two procedures for parameter identification in the standard quasi-dynamic testing of solar thermal collectors: multilinear regression (MLR) and dynamic parameter identification (DPI). The main advantage of DPI is that it is more flexible with respect to the collector model, allowing the use of more sophisticated thermal models and the reduction of testing time. However, most of the implementations available in the literature require non-free close source software, making its replication a difficult task for most testing laboratories. In this work we show a specific implementation of a dynamic parameter identification procedure for a flat plate collector. The algorithm is described in detail, and we also provided a free open-source code in Matlab, facilitating the reproduction of our work and attempting to extend the use of this procedure. We validated its implementations against the standard MLR, comparing the model parameter’s values, the efficiency curve and the useful power produced by the collector under the Reporting Standard Conditions defined by the ISO 9806 standard. The measurements were taken in local test facility that compliant with the ISO 9806:2017 requirements.