Pesticides are toxic chemicals/products that are widely used for pest control. The most widely used type of pesticides is insecticides, fungicides and herbicides. Their continued use has been associated with undesired effects to non-target organisms thus raising environmental concerns worldwide. The problem however, is complex to integrate as there are number of processes that could contribute to the undesired effects. One of the problems is the lack of object-oriented and open source ecological tools that could be used to model the complex interaction of pesticides in the environment and their effects to non-target organisms e.g., frogs. Ecological models could save time as they could be used for management of complex interaction in the environment. The aim of the present study was therefore to add to the available literature, an ecological modeling tool that could be used to model this complex interaction of pesticides and the environment either for research or registration purposes. In this view, PestTox, which is an object-oriented and open-source model, was developed. The model is written in standard C++ language to model this complex interaction. PestTox adopted PestLCI model so that sub-models (objects) could be integrated to it. New equations for modeling washoff, photo-degradation, and pesticide-induced mortality rates were added to PestTox. The model runs on Linux, OS X, and Windows operating systems. It utilizes open source programs; Universal simulator, R, and Notepad, as such it remains open source. This model could be of interest to those involved in ecological modeling, modeling fate and transport of pesticides, data science, and management framework to evaluate potential effects of using pesticides in agricultural settings.