The group stage was held at the Bill Graham Civic Auditorium in San Francisco, California. The group stage was played in a best of one double round-robin format, where each team played every other team in their group twice, with the top two teams from each of the four groups advancing to the knockout stage.
Tiebreaking matches were played in groups A and C.
The Cinderella story of the tournament was the run of Albus NoX Luna, the CIS champions who became the first wildcard team to make it to the quarterfinals in the history of the League of Legends World Championship. European first seed G2 Esports underperformed in this group, while ROX Tigers, the first seed from Korea, won the group as expected, but had to do so by defeating Albus NoX Luna in a tiebreaker game.
Group B’s deciding matches all occurred on the last day, when all teams except for the Korean first seed SK Telecom T1 had 2–3 records. In the end, it was Cloud9, the sole North American team to move on, that moved on after exploiting the inconsistent play of the Chinese and Taiwanese teams. I May was also hurt when one of its players was suspended for one match on the last day and fined $2000 for abusive behavior in online games. During Cloud 9’s match against Flash Wolves, Zachary “Sneaky” Scuderi killed 690 minions, which set a new record for this statistic at worlds.
Group C was the only group without a Korean team seeded first. Its two qualifiers were both considered championship favorites, since H2K0Gaming was a strong European team and EDward Gaming was a strong Chinese team. Despite a 1–2 showing in the first week, H2K managed to make the quarterfinals at the top of its group by winning four straight matches, including a tiebreaker against EDward Gaming, to become the only European team to move on.
Group D was considered to be the group of death because it had three top Korean, Chinese, and North American teams, and a strong European team. Samsung Galaxy, would convincingly win the group with help from the strong play of Kang “Ambition” Chang-yong. Royal Never Give Up defeated the North American champions TSM to even their records at 3–3 and win the head-to-head tiebreaker to move on to the quarterfinals.