Set in White Wolf Publishing's World of Darkness, the game is based on White Wolf's role-playing game Vampire: The Masquerade and follows either a male or female character who is killed and subsequently revived as a fledgling vampire. The game depicts the fledgling's journey through 21st-century Los Angeles to uncover the truth behind a recently discovered relic that heralds the end of all vampires.
Bloodlines is presented from first- and third-person perspectives. The player assigns their character to one of several vampire clans—each with unique powers, customizes their combat and dialog abilities and progresses through Bloodlines using violent and nonviolent methods. The selection of clan affects how the player is perceived in the game world, and which powers and abilities they possess; this opens up different avenues of exploration and methods of interacting with or manipulating other characters. The player is able to complete side missions away from the primary storyline by moving freely between the available hubs: Santa Monica, Hollywood, downtown Los Angeles, and Chinatown.