This guide was made by Buster WolfBuster Wolf.

This will list how to unlock all 55 characters for Free mode. Story mode stages will be labeled by story and battle number (ex Naotora Ii is unlocked in Defense of Tōtōmi which is Legend of Kantō 2 or Battle of Okehazama which is Legend of Tokugawa 1). You can unlock characters in Chronicles Mode when you have 4 bars of friendship value with them. Characters are listed by the game that they debuted in, characters from Chronicles 2nd are grouped with Samurai Warriors 3 characters.

Samurai Warriors 1

Character Requirement
Yukimura Sanada Default
Keiji Maeda Default
Nobunaga Oda Default
Mitsuhide Akechi Oda 2 or Shikoku 1
Goemon Ishikawa Chronicles Mode
Kenshin Uesugi Uesugi 1
Oichi Default
Okuni Chronicles Mode
Kunoichi Default
Magoichi Saika Tōhoku 2 or Oda 2
Shingen Takeda Default
Masamune Date Land United 5 or Tōhoku 1
Default
Hanzō Hattori Sanada 5 (Eastern) or Tokugawa 1
Ranmaru Mori Oda 4
Hideyoshi Hashiba Default
Yoshimoto Imagawa Tokugawa 1
Tadakatsu Honda Land United 5 or Tokugawa 1
Ina Sanada 4 or Tokugawa 2

Samurai Warriors 2

Character Requirement
Ieyasu Tokugawa Tokugawa 1 or Oda 4
Mitsunari Ishida Default
Nagamasa Azai Oda 2
Sakon Shima Default
Yoshihiro Shimazu Kyūshū 1 or Land United 5
Ginchiyo Tachibana Land United 5
Kanetsugu Naoe Sanada 3 or Uesugi 1
Nene Oda 2
Kotarō Fūma Default
Musashi Miyamoto Chronicles Mode
Toshiie Maeda Default
Motochika Chōsokabe Oda 8 or Shikoku 1
Gracia Oda 8 or Shikoku 1
Kojirō Sasaki Chronicles Mode
Katsuie Shibata Default

Samurai Warriors 3

Character Requirement
Kiyomasa Katō Land United 1
Kanbei Kuroda Oda 4
Muneshige Tachibana Land United 5
Kai Default
Ujiyasu Hōjō Default
Hanbei Takenaka Oda 3
Motonari Mōri Default
Aya Uesugi 1
Masanori Fukushima Land United 1
Takatora Tōdō Kinki 1 or Land United 4
Naotora Ii Kantō 2 or Tokugawa 1
Munenori Yagyū Oda 3 or Shikoku 4

Samurai Warriors 4

Character Requirement
Nobuyuki Sanada Default
Yoshitsugu Ōtani Kinki 1, Land United 1 or Sanada 4
Hisahide Matsunaga Oda 3
Kojūrō Katakura Land United 5 or Tōhoku 1
Kagekatsu Uesugi Sanada 4 or Uesugi 1
Takakage Nobayakawa Default
Koshōshō Oda 8 or Shikoku 3
Toyohisa Shimazu Default
Lady Hayakawa Default