What is a video game story and how to write one? The purpose of this thesis is to find the answer to these questions. This is done by laying out different practical tools for developing the different elements of game stories and by using these tools for analyzing and further development of a case. To be able to write exciting and immersive video game stories, various theorists argue that the writer must have both game designing and writing skills – The writer and game designer must merge together into a game designer/writer hybrid. The theory presented in this thesis is therefore a combination of both narrative and game design methods that when merged shape the practical tools for video game story writing. The thesis divides video game stories into three categories: Game universe, characters and plot. These three categories are represented in three individual parts of the thesis. The three parts present different theories that form the foundation for the practical tool. Each of the three parts is therefore a set of tools for the individual content of the respective part, but because writing a game story is a dynamic process, the different methods can also be combined and work together. The thesis examines the game universe in four dimensions: The physical, the temporal, the environmental and the ethical dimension. By being aware of these dimensions and by making them work together, it is possible to create a game universe which supports the game play as well as compels the player and thereby making him/her wanting to spend more time in the game universe. Characters are divided into player characters and non-player characters. Depending on which of the two character types the game designer/writer is creating, different psychological methods can be used to create different experiences for the player. By using a so called character diamond it is possible to create an easily accessible foundation for each character. Further more different techniques such as character progression can be used to make a game’s characters an interesting acquaintance. There are various ways of structuring a video game plot. By utilizing classic techniques known from literature and film, a plot, where the suspense falls and rises in a well-verified but not very interactive manner, can be produced. To make more player-driven plots, different topographies can be used to structure the plot and to make sure a game plot does not have loose ends etc. To ensure that the player does not get lost and/or lose interest in the story various rules of design can be utilized. Through a practical analysis and further development of the game Just Cause 2 – Mobile, the tools presented in the theoretical part of the thesis are tested and evaluated. By using the tools for improving an actual game, it becomes clear that all the tools have relevancy and actually work when creating game stories, but that some tools become more central than others. Furthermore, through the practical part of the thesis, it is also underlined that it is very important when writing video game stories that the writer has have knowledge of both the writing as well as game designing techniques. It is also important that a game story is very well though through in all aspects to avoid giving the player a frustrating experience and to create a fun and immersive game.