Grand Theft Auto IV gameplay takes place through missions that Niko undertakes for less than savory Liberty City residents. While missions from a particular mission provider are given in order, players do have the option of choosing who to work for. As a result, missions do not necessarily take place in the same order as that listed in any walkthrough. Many of the missions that are played later in the game are played outside of their specific chapters. 

Missions follow a general pattern. Niko will receive a phone call on his cell, or meet with someone who provides him with a task. Niko then needs to drive to the specified location to perform a directed action, e.g., fighting, driving, delivery, etc. Upon completion, Niko either places or receives another phone call letting him know that the mission has been completed successfully. Any reward affiliated with the completed mission is then dispensed.

This Grand Theft Auto IV walkthrough provides text and video details for each mission in the main storyline, as well as guidance for the non-story missions. 

Grand Theft Auto IV follows the immigration of Niko Bellic to the United States from Eastern Europe. Prior to the game's story, Niko fought in the Bosnian War and was betrayed by one of his unit members. This betrayal caused the death of most of the unit. Niko is now obsessed with attaining revenge. Poor circumstances after the war's ending led to Niko working for Ray Bulgarin in human trafficking. This ended with Niko leaving Europe to escape the reach of Bulgarin. After spending time in the merchant navy, Niko immigrated to Liberty City, after listening to his cousin Roman's stories of living a life of luxury.