All 12 Pac-12 schools were eligible to participate in the tournament. Teams were seeded by conference record, with a tiebreaker system used to seed teams with identical conference records. As a result, the top four teams receive a bye to the quarterfinals of the tournament.
Tie-breaking procedures for determining all tournament seeding was:
For two-team tie
1. Results of head-to-head competition during the regular season.
2. Each team's record (won-lost percentage) vs. the team occupying the highest position in the final regular standings, and then continuing down through the standings until one team gains an advantage.
When arriving at another group of tied teams while comparing records, use each team's record (won-lost percentage) against the collective tied teams as a group (prior to that group's own tie-breaking procedure), rather than the performance against individual tied teams.
3. Won-lost percentage against all Division I opponents.
4. Coin toss conducted by the Commissioner or designee.
For multiple-team tie
1. Results (won-lost percentage) of collective head-to-head competition during the regular season among the tied teams.
2. If more than two teams are still tied, each of the tied team's record (won-lost percentage) vs. the team occupying the highest position in the final regular season standings, and then continuing down through the standings, eliminating teams with inferior records, until one team gains an advantage.
When arriving at another group of tied teams while comparing records, use each team's record (won-lost percentage) against the collective tied teams as a group (prior to that group's own tie-breaking procedure), rather than the performance against individual tied teams.
After one team has an advantage and is seeded, all remaining teams in the multiple-team tie-breaker will repeat the multiple-team tie-breaking procedure.
If at any point the multiple-team tie is reduced to two teams, the two-team tie-breaking procedure will be applied.
3. Won-lost percentage against all Division I opponents.
4. Coin toss conducted by the Commissioner or designee.
Tournament winner Oregon was awarded the automatic bid to the 2019 NCAA Division I men's basketball tournament and was the 12 seed in the South Regional. They lost in the regional semi-finals to the 1 seed and eventual national champion, Virginia.
Regular season winner Washington gained an at-large bid to the 2019 tournament as a 9 seed in the Midwest
Arizona State received an at-large bid in the First Four as an 11 seed in the West.